Polymerizable compounds and the use thereof in liquid-crystal displays

ABSTRACT

The present invention relates to polymerizable compounds, to processes and intermediates for the preparation thereof, to liquid-crystal (LC) media comprising them, and to the use of the polymerizable compounds and LC media for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the polymer sustained alignment type.

The present invention relates to polymerizable compounds, to processes and intermediates for the preparation thereof, to liquid-crystal (LC) media comprising them, and to the use of the polymerizable compounds and LC media for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the polymer sustained alignment type.

BACKGROUND OF THE INVENTION

The liquid-crystal displays (LC displays) used at present are usually those of the TN (“twisted nematic”) type. However, these have the disadvantage of a strong viewing-angle dependence of the contrast.

In addition, so-called VA (“vertically aligned”) displays are known which have a broader viewing angle. The LC cell of a VA display contains a layer of an LC medium between two transparent electrodes, where the LC medium usually has a negative dielectric anisotropy. In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment. On application of an electrical voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place.

Furthermore, OCB (“optically compensated bend”) displays are known which are based on a birefringence effect and have an LC layer with a so-called “bend” alignment and usually positive dielectric anisotropy. On application of an electrical voltage, a realignment of the LC molecules perpendicular to the electrode surfaces takes place. In addition, OCB displays normally contain one or more birefringent optical retardation films in order to prevent undesired transparency to light of the bend cell in the dark state. OCB displays have a broader viewing angle and shorter response times compared with TN displays.

Also known are so-called IPS (“in-plane switching”) displays, which contain an LC layer between two substrates, where the two electrodes are arranged on only one of the two substrates and preferably have intermeshed, comb-shaped structures. On application of a voltage to the electrodes, an electric field which has a significant component parallel to the LC layer is thereby generated between them. This causes realignment of the LC molecules in the layer plane.

Furthermore, so-called FFS (“fringe-field switching”) displays have been reported (see, inter alia, S. H. Jung et al., Jpn. J. Appl. Phys., Volume 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which structured in a comb-shaped manner and the other is unstructured. A strong, so-called “fringe field” is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component. FFS displays have a low viewing-angle dependence of the contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy, and an alignment layer, usually of polyimide, which provides planar alignment to the molecules of the LC medium.

FFS displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, transistors (for example thin-film transistors (“TFTs”)), while in the case of passive-matrix displays, individual pixels are usually addressed by the multiplex method, as known from the prior art.

Furthermore, FFS displays have been disclosed (see S. H. Lee et al., Appl. Phys. Lett. 73(20), 1998, 2882-2883 and S. H. Lee et al., Liquid Crystals 39(9), 2012, 1141-1148), which have similar electrode design and layer thickness as FFS displays, but comprise a layer of an LC medium with negative dielectric anisotropy instead of an LC medium with positive dielectric anisotropy. The LC medium with negative dielectric ansiotropy shows a more favourable director orientation that has less tilt and more twist orientation compared to the LC medium with positive dielectric anisotropy, as a result of which these displays have a higher transmission. The displays further comprise an alignment layer, preferably of polyimide provided on at least one of the substrates that is in contact with the LC medium and induces planar alignment of the LC molecules of the LC medium. These displays are also known as “Ultra Brightness FFS (UB-FFS)” mode displays. These displays require an LC medium with high reliability.

The term “reliability” as used hereinafter means the quality of the performance of the display during time and with different stress loads, such as light load, temperature, humidity, voltage, and comprises display effects such as image sticking (area and line image sticking), mura, yogore etc. which are known to the skilled person in the field of LC displays. As a standard parameter for categorising the reliability usually the voltage holding ration (VHR) value is used, which is a measure for maintaining a constant electrical voltage in a test display. The higher the VHR value, the better the reliability of the LC medium.

In VA displays of the more recent type, uniform alignment of the LC molecules is restricted to a plurality of relatively small domains within the LC cell. Disclinations may exist between these domains, also known as tilt domains. VA displays having tilt domains have, compared with conventional VA displays, a greater viewing-angle independence of the contrast and the grey shades. In addition, displays of this type are simpler to produce since additional treatment of the electrode surface for uniform alignment of the molecules in the switched-on state, such as, for example, by rubbing, is no longer necessary. Instead, the preferential direction of the tilt or pretilt angle is controlled by a special design of the electrodes.

In so-called MVA (“multidomain vertical alignment”) displays, this is usually achieved by the electrodes having protrusions which cause a local pretilt. As a consequence, the LC molecules are aligned parallel to the electrode surfaces in different directions in different, defined regions of the cell on application of a voltage. “Controlled” switching is thereby achieved, and the formation of interfering disclination lines is prevented. Although this arrangement improves the viewing angle of the display, it results, however, in a reduction in its transparency to light. A further development of MVA uses protrusions on only one electrode side, while the opposite electrode has slits, which improves the transparency to light. The slitted electrodes generate an inhomogeneous electric field in the LC cell on application of a voltage, meaning that controlled switching is still achieved. For further improvement of the transparency to light, the separations between the slits and protrusions can be increased, but this in turn results in a lengthening of the response times. In so-called PVA (“patterned VA”) displays, protrusions are rendered completely superfluous in that both electrodes are structured by means of slits on the opposite sides, which results in increased contrast and improved transparency to light, but is technologically difficult and makes the display more sensitive to mechanical influences (“tapping”, etc.). For many applications, such as, for example, monitors and especially TV screens, however, a shortening of the response times and an improvement in the contrast and luminance (transmission) of the display are demanded.

A further development are displays of the so-called PS (“polymer sustained”) or PSA (“polymer sustained alignment”) type, for which the term “polymer stabilised” is also occasionally used. In these, a small amount (for example 0.3% by weight, typically <1% by weight) of one or more polymerizable, compound(s), preferably polymerizable monomeric compound(s), is added to the LC medium and, after filling the LC medium into the display, is polymerized or crosslinked in situ, usually by UV photopolymerization, optionally while a voltage is applied to the electrodes of the display. The polymerization is carried out at a temperature where the LC medium exhibits a liquid crystal phase, usually at room temperature. The addition of polymerizable mesogenic or liquid-crystalline compounds, also known as reactive mesogens or “RMs”, to the LC mixture has proven particularly suitable.

Unless indicated otherwise, the term “PSA” is used hereinafter when referring to displays of the polymer sustained alignment type in general, and the term “PS” is used when referring to specific display modes, like PS-VA, PS-TN and the like.

Also, unless indicated otherwise, the term “RM” is used hereinafter when referring to a polymerizable mesogenic or liquid-crystalline compound.

In the meantime, the PS(A) principle is being used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS and PS-TN displays are known. The polymerization of the RMs preferably takes place with an applied voltage in the case of PS-VA and PS-OCB displays, and with or without, preferably without, an applied voltage in the case of PS-IPS displays. As can be demonstrated in test cells, the PS(A) method results in a pretilt in the cell. In the case of PS-OCB displays, for example, it is possible for the bend structure to be stabilised so that an offset voltage is unnecessary or can be reduced. In the case of PS-VA displays, the pretilt has a positive effect on response times. For PS-VA displays, a standard MVA or PVA pixel and electrode layout can be used. In addition, however, it is also possible, for example, to manage with only one structured electrode side and no protrusions, which significantly simplifies production and at the same time results in very good contrast at the same time as very good transparency to light.

Furthermore, the so-called posi-VA displays (“positive VA”) have proven to be a particularly suitable mode. Like in classical VA displays, the initial orientation of the LC molecules in posi-VA displays is homeotropic, i.e. substantially perpendicular to the substrates, in the initial state when no voltage is applied. However, in contrast to classical VA displays, in posi-VA displays LC media with positive dielectric anisotropy are used. Like in the usually used IPS displays, the two electrodes in posi-VA displays are arranged on only one of the two substrates, and preferably exhibit intermeshed and comb-shaped (interdigital) structures. By application of a voltage to the interdigital electrodes, which create an electrical field that is substantially parallel to the layer of the LC medium, the LC molecules are transferred into an orientation that is substantially parallel to the substrates. In posi-VA displays polymer stabilisation, by addition of RMs to the LC medium which are polymerized in the display, has also proven to be advantageous, as a significant reduction of the switching times could thereby<be realised.

PS-VA displays are described, for example, in EP 1 170 626 A2, U.S. Pat. No. 6,861,107, U.S. Pat. No. 7,169,449, US 2004/0191428 A1, US 2006/0066793 A1 and US 2006/0103804 A1. PS-OCB displays are described, for example, in T.-J-Chen et al., Jpn. J. Appl. Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C-Chien, Jpn. J. Appl. Phys. 43, 2004, 7643-7647. PS-IPS displays are described, for example, in U.S. Pat. No. 6,177,972 and Appl. Phys. Lett. 1999, 75(21), 3264. PS-TN displays are described, for example, in Optics Express 2004, 12(7), 1221.

Like the conventional LC displays described above, PSA displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, transistors (for example thin-film transistors (“TFTs”)), while in the case of passive-matrix displays, individual pixels are usually addressed by the multiplex method, as known from the prior art.

The PSA display may also comprise an alignment layer on one or both of the substrates forming the display cell. The alignment layer is usually applied on the electrodes (where such electrodes are present) such that it is in contact with the LC medium and induces initial alignment of the LC molecules. The alignment layer may comprise or consist of, for example, a polyimide, which may also be rubbed, or may be prepared by a photoalignment method.

In particular for monitor and especially TV applications, optimisation of the response times, but also of the contrast and luminance (thus also transmission) of the LC display continues to be demanded. The PSA method can provide significant advantages here. In particular in the case of PS-VA, PS-IPS, PS-FFS and PS-posi-VA displays, a shortening of the response times, which correlate with a measurable pretilt in test cells, can be achieved without significant adverse effects on other parameters.

Prior art has suggested biphenyl diacrylates or dimethacrylates, which are optionally fluorinated as RMs for use in PSA displays

However, the problem arises that not all combinations consisting of an LC mixture and one or more RMs are suitable for use in PSA displays because, for example, an inadequate tilt or none at all becomes established or since, for example, the so-called “voltage holding ratio” (VHR or HR) is inadequate for TFT display applications. In addition, it has been found that, on use in PSA displays, the LC mixtures and RMs known from the prior art do still have some disadvantages. Thus, not every known RM which is soluble in LC mixtures is suitable for use in PSA displays. In addition, it is often difficult to find a suitable selection criterion for the RM besides direct measurement of the pretilt in the PSA display. The choice of suitable RMs becomes even smaller if polymerization by means of UV light without the addition of photoinitiators is desired, which may be advantageous for certain applications.

In addition, the selected combination of LC host mixture/RM should have the lowest possible rotational viscosity and the best possible electrical properties. In particular, it should have the highest possible VHR. In PSA displays, a high VHR after irradiation with UV light is particularly necessary since UV exposure is a requisite part of the display production process, but also occurs as normal exposure during operation of the finished display.

In particular, it would be desirable to have available novel materials for PSA displays which produce a particularly small pretilt angle. Preferred materials here are those which produce a lower pretilt angle during polymerization for the same exposure time than the materials known to date, and/or through the use of which the (higher) pretilt angle that can be achieved with known materials can already be achieved after a shorter exposure time. The production time (“tact time”) of the display could thus be shortened and the costs of the production process reduced.

A further problem in the production of PSA displays is the presence or removal of residual amounts of unpolymerized RMs, in particular after the polymerization step for production of the pretilt angle in the display. For example, unreacted RMs of this type may adversely affect the properties of the display by, for example, polymerising in an uncontrolled manner during operation after finishing of the display.

Thus, the PSA displays known from the prior art often exhibit the undesired effect of so-called “image sticking” or “image burn”, i.e. the image produced in the LC display by temporary addressing of individual pixels still remains visible even after the electric field in these pixels has been switched off or after other pixels have been addressed.

This “image sticking” can occur on the one hand if LC host mixtures having a low VHR are used. The UV component of daylight or the backlighting can cause undesired decomposition reactions of the LC molecules therein and thus initiate the production of ionic or free-radical impurities. These may accumulate, in particular, at the electrodes or the alignment layers, where they may reduce the effective applied voltage. This effect can also be observed in conventional LC displays without a polymer component.

In addition, an additional “image sticking” effect caused by the presence of unpolymerized RMs is often observed in PSA displays. Uncontrolled polymerization of the residual RMs is initiated here by UV light from the environment or by the backlighting. In the switched display areas, this changes the tilt angle after a number of addressing cycles. As a result, a change in transmission in the switched areas may occur, while it remains unchanged in the unswitched areas.

It is therefore desirable for the polymerization of the RMs to proceed as completely as possible during production of the PSA display and for the presence of unpolymerized RMs in the display to be excluded as far as possible or reduced to a minimum. Thus, RMs and LC mixtures are required which enable or support highly effective and complete polymerization of the RMs. In addition, controlled reaction of the residual RM amounts would be desirable. This would be simpler if the RM polymerized more rapidly and effectively than the compounds known to date.

A further problem that has been observed in the operation of PSA displays is the stability of the pretilt angle. Thus, it was observed that the pretilt angle, which was generated during display manufacture by polymerising the RM as described above, does not remain constant but can deteriorate after the display was subjected to voltage stress during its operation. This can negatively affect the display performance, e.g. by increasing the black state transmission and hence lowering the contrast.

Another problem to be solved is that the RMs of prior art do often have high melting points, and do only show limited solubility in many currently common LC mixtures, and therefore frequently tend to spontaneously crystallise out of the mixture. In addition, the risk of spontaneous polymerization prevents the LC host mixture being warmed in order to dissolve the polymerizable component, meaning that the best possible solubility even at room temperature is necessary. In addition, there is a risk of separation, for example on introduction of the LC medium into the LC display (chromatography effect), which may greatly impair the homogeneity of the display. This is further increased by the fact that the LC media are usually introduced at low temperatures in order to reduce the risk of spontaneous polymerization (see above), which in turn has an adverse effect on the solubility.

Another problem observed in prior art is that the use of conventional LC media in LC displays, including but not limited to displays of the PSA type, often leads to the occurrence of mura in the display, especially when the LC medium is filled in the display cell manufactured using the one drop filling (ODF) method. This phenomenon is also known as “ODF mura”. It is therefore desirable to provide LC media which lead to reduced ODF mura.

Another problem observed in prior art is that LC media for use in PSA displays, including but not limited to displays of the PSA type, do often exhibit high viscosities and, as a consequence, high switching times. In order to reduce the viscosity and switching time of the LC medium, it has been suggested in prior art to add LC compounds with an alkenyl group. However, it was observed that LC media containing alkenyl compounds often show a decrease of the reliability and stability, and a decrease of the VHR especially after exposure to UV radiation. Especially for use in PSA displays this is a considerable disadvantage, because the photo-polymerization of the RMs in the PSA display is usually carried out by exposure to UV radiation, which may cause a VHR drop in the LC medium.

There is thus still a great demand for PSA displays and LC media and polymerizable compounds for use in such displays, which do not show the drawbacks as described above, or only do so to a small extent, and have improved properties.

In particular, there is a great demand for PSA displays, and LC media and polymerizable compounds for use in such PSA displays, which enable a high specific resistance at the same time as a large working-temperature range, short response times, even at low temperatures, and a low threshold voltage, a low pretilt angle, a multiplicity of grey shades, high contrast and a broad viewing angle, have high reliability and high values for the “voltage holding ratio” (VHR) after UV exposure, and, in case of the polymerizable compounds, have low melting points and a high solubility in the LC host mixtures. In PSA displays for mobile applications, it is especially desired to have available LC media that show low threshold voltage and high birefringence.

The invention is provides novel suitable materials, in particular RMs and LC media comprising the same, for use in PSA displays, which do not have the disadvantages indicated above or do so to a reduced extent.

In particular, the invention provides RMs, and LC media comprising them, for use in PSA displays, which enable very high specific resistance values, high VHR values, high reliability, low threshold voltages, short response times, high birefringence, show good UV absorption especially at longer wavelengths, enable quick and complete polymerization of the RMs, allow the generation of a low pretilt angle as quickly as possible, enable a high stability of the pretilt even after longer time and/or after UV exposure, reduce or prevent the occurrence of “image sticking” and “ODF mura” in the display, and in case of the RMs polymerize as rapidly and completely as possible and show a high solubility in the LC media which are typically used as host mixtures in PSA displays.

The invention also provides RMs, in particular for optical, electro-optical and electronic applications, and suitable processes and intermediates for the preparation thereof.

In particular, it has been found, surprisingly, that, the use of RMs of formula I as described hereinafter allows achieving the advantageous effects as mentioned above. These compounds are characterized in that they have a meta-terphenyl mesogenic core to which two or more reactive groups are attached to the outer benzene rings, but not on the central ring, and wherein at least one of these reactive groups is attached to the benzene ring directly, and at least one of these reactive groups is attached to the benzene ring via a spacer group.

It was surprisingly found that the use of these RMs, and of LC media comprising them, in PSA displays facilitates a quick and complete UV-photopolymerization reaction in particular at longer UV wavelengths in the range from 300-380 nm and especially above 340 nm, even without the addition of photoinitiator, leads to a fast generation of a large and stable pretilt angle, reduces image sticking and ODF mura in the display, leads to a high reliability and a high VHR value after UV photopolymerization, especially in case of LC host mixtures containing LC compounds with an alkenyl group, and enables to achieve fast response times, a low threshold voltage and a high birefringence.

In addition, the RMs according to the invention have low melting points, good solubility in a wide range of LC media, especially in commercially available LC host mixtures for PSA use, and a low tendency to crystallisation. Besides, they show good absorption at longer UV wavelengths, in particular in the range from 300-380 nm, and enable a quick and complete polymerization with small amounts of residual, unreacted RMs in the cell.

WO 2010/131600 A1 discloses polymerizable compounds with a meta-terphenyl structure and their use in PSA displays, but does neither disclose nor suggest polymerizable compounds as disclosed and claimed hereinafter.

SUMMARY OF THE INVENTION

The invention relates to polymerizable compounds of formula I

in which the individual radicals have the following meanings

-   R denotes P-Sp^(b)-, H or has one of the meanings given for L, -   Sp^(a), Sp^(b) denote, on each occurrence identically or     differently, a spacer group or a single bond, -   P denotes, on each occurrence identically or differently, a     polymerizable group, -   L F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to     25 C atoms, wherein one or more non-adjacent CH₂-groups are     optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in     such a manner that O- and/or S-atoms are not directly connected with     each other, and wherein one or more H atoms are each optionally     replaced by F or Cl, -   r is 0, 1, 2, 3 or 4, -   s is 0, 1, 2 or 3,     wherein at least one of Sp^(a) and Sp^(b) is a single bond and at     least one of Sp^(a) and Sp^(b) is different from a single bond.

The invention further relates to the use of compounds of formula I as polymerizable compounds in LC media and LC displays, especially in the LC medium, active layer or alignment layer of an LC display, wherein the LC displays are preferably PSA displays.

The invention further relates to methods for preparing compounds of formula I, and to novel intermediates used or obtained in these methods.

The invention furthermore relates to an LC medium comprising one or more compounds of formula I.

The invention furthermore relates to an LC medium comprising one or more polymerizable compounds, at least one of which is a compound of formula I.

The invention furthermore relates to an LC medium comprising

-   -   a polymerizable component A) comprising, preferably consisting         of, one or more polymerizable compounds, at least one of which         is a compound of formula I, and     -   a liquid-crystalline component B), hereinafter also referred to         as “LC host mixture”, comprising, preferably consisting of, one         or more mesogenic or liquid-crystalline compounds.

The liquid-crystalline component B) of an LC medium according to the present invention is hereinafter also referred to as “LC host mixture”, and preferably comprises one or more, preferably at least two mesogenic or LC compounds selected from low-molecular-weight compounds which are unpolymerizable.

The invention furthermore relates to an LC medium as described above and below, wherein the LC host mixture or component B) comprises at least one mesogenic or LC compound comprising an alkenyl group.

The invention furthermore relates to an LC medium or LC display as described above, wherein the compounds of formula I, or the polymerizable compounds of component A), are polymerized.

The invention furthermore relates to a process for preparing an LC medium as described above and below, comprising the steps of mixing one or more mesogenic or LC compounds, or an LC host mixture or LC component B) as described above and below, with one or more compounds of formula I, and optionally with further LC compounds and/or additives.

The invention furthermore relates to the use of compounds of formula I and LC media according to the invention in PSA displays, in particular the use in PSA displays containing an LC medium, for the production of a tilt angle in the LC medium by in-situ polymerization of the compound(s) of the formula I in the PSA display, preferably in an electric or magnetic field.

The invention furthermore relates to an LC display comprising one or more compounds of formula I or an LC medium according to the invention, in particular a PSA display, particularly preferably a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-posi-VA or PS-TN display.

The invention furthermore relates to an LC display comprising a polymer obtainable by polymerization of one or more compounds of formula I or of a polymerizable component A) as described above, or comprising an LC medium according to the invention, which is preferably a PSA display, very preferably a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-posi-VA or PS-TN display.

The invention furthermore relates to an LC display of the PSA type comprising two substrates, at least one which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and located between the substrates a layer of an LC medium that comprises one or more polymerizable compounds and an LC component as described above and below, wherein the polymerizable compounds are polymerized between the substrates of the display.

The invention furthermore relates to a process for manufacturing an LC display as described above and below, comprising the steps of filling or otherwise providing an LC medium, which comprises one or more polymerizable compounds as described above and below, between the substrates of the display, and polymerising the polymerizable compounds.

The PSA displays according to the invention have two electrodes, preferably in the form of transparent layers, which are applied to one or both of the substrates. In some displays, for example in PS-VA, PS-OCB or PS-TN displays, one electrode is applied to each of the two substrates. In other displays, for example in PS-posi-VA, PS-IPS or PS-FFS or PS-UB-FFS displays, both electrodes are applied to only one of the two substrates.

In a preferred embodiment the polymerizable component is polymerized in the LC display while a voltage is applied to the electrodes of the display.

The polymerizable compounds of the polymerizable component are preferably polymerized by photo-polymerization, very preferably by UV photo-polymerization.

DETAILED DESCRIPTION OF THE INVENTION

Unless stated otherwise, the compounds of formula I are preferably selected from achiral compounds.

As used herein, the terms “active layer” and “switchable layer” mean a layer in an electrooptical display, for example an LC display, that comprises one or more molecules having structural and optical anisotropy, like for example LC molecules, which change their orientation upon an external stimulus like an electric or magnetic field, resulting in a change of the transmission of the layer for polarized or unpolarized light.

As used herein, the terms “tilt” and “tilt angle” will be understood to mean a tilted alignment of the LC molecules of an LC medium relative to the surfaces of the cell in an LC display (here preferably a PSA display). The tilt angle here denotes the average angle (<90°) between the longitudinal molecular axes of the LC molecules (LC director) and the surface of the plane-parallel outer plates which form the LC cell. A low value for the tilt angle (i.e. a large deviation from the 90° angle) corresponds to a large tilt here. A suitable method for measurement of the tilt angle is given in the examples. Unless indicated otherwise, tilt angle values disclosed above and below relate to this measurement method.

As used herein, the terms “reactive mesogen” and “RM” will be understood to mean a compound containing a mesogenic or liquid crystalline skeleton, and one or more functional groups attached thereto which are suitable for polymerization and are also referred to as “polymerizable group” or “P”.

Unless stated otherwise, the term “polymerizable compound” as used herein will be understood to mean a polymerizable monomeric compound.

As used herein, the term “low-molecular-weight compound” will be understood to mean to a compound that is monomeric and/or is not prepared by a polymerization reaction, as opposed to a “polymeric compound” or a “polymer”.

As used herein, the term “unpolymerizable compound” will be understood to mean a compound that does not contain a functional group that is suitable for polymerization under the conditions usually applied for the polymerization of the RMs.

The term “mesogenic group” as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerization. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic or LC compounds is given in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

The term “spacer group”, hereinafter also referred to as “Sp”, as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. As used herein, the terms “spacer group” or “spacer” mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerizable group(s) in a polymerizable mesogenic compound.

Above and below,

denotes a trans-1,4-cyclohexylene ring, and

denotes a 1,4-phenylene ring.

Above and below “organic group” denotes a carbon or hydrocarbon group.

“Carbon group” denotes a mono- or polyvalent organic group containing at least one carbon atom, where this either contains no further atoms (such as, for example, —C≡C—) or optionally contains one or more further atoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge (for example carbonyl, etc.). The term “hydrocarbon group” denotes a carbon group which additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge.

“Halogen” denotes F, Cl, Br or I.

—CO—, —C(═O)— and —C(O)— denote a carbonyl group, i.e.

A carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. A carbon or hydrocarbon radical having more than 3 C atoms can be straight-chain, branched and/or cyclic and may also contain spiro links or condensed rings.

The terms “alkyl”, “aryl”, “heteroaryl”, etc., also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc.

The term “aryl” denotes an aromatic carbon group or a group derived therefrom. The term “heteroaryl” denotes “aryl” as defined above, containing one or more heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge.

Preferred carbon and hydrocarbon groups are optionally substituted, straight-chain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25, C atoms, wherein one or more C atoms may also be replaced by hetero atoms, preferably selected from N, O, S, Se, Te, Si and Ge.

Further preferred carbon and hydrocarbon groups are C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl, C₂-C₂₀ alkynyl, C₃-C₂₀ allyl, C₄-C₂₀ alkyldienyl, C₄-C₂₀ polyenyl, C₆-C₂₀ cycloalkyl, C₄-C₁₅ cycloalkenyl, C₆-C₃₀ aryl, C₆-C₃₀ alkylaryl, C₆-C₃₀ arylalkyl, C₆-C₃₀ alkylaryloxy, C₆-C₃₀ arylalkyloxy, C₂-C₃₀ heteroaryl, C₂-C₃₀ heteroaryloxy.

Particular preference is given to C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl, C₆-C₂₅ aryl and C₂-C₂₅ heteroaryl.

Further preferred carbon and hydrocarbon groups are straight-chain, branched or cyclic alkyl having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN and in which one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by —C(R^(x))═C(R^(x))—, —C≡C—, —N(R^(x))—, —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another.

R^(x) preferably denotes H, F, Cl, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-adjacent C atoms may be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— and in which one or more H atoms may be replaced by F or Cl, or denotes an optionally substituted aryl or aryloxy group with 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group with 2 to 30 C atoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, etc.

Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxyethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy, n-dodecoxy, etc.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.

Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se.

Particular preference is given to mono-, bi- or tricyclic aryl groups having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6- or 7-membered aryl and heteroaryl groups, in which, in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and/or S atoms are not linked directly to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1,1′:3′,1″]terphenyl-2′-yl, naphthyl, anthracene, binaphthyl, phenanthrene, 9,10-dihydro-phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1,2-thiazole, 1,3-thiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, 1,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,3-triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, or condensed groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazothiophene, or combinations of these groups.

The aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e. contain only one ring (such as, for example, cyclohexane), or polycyclic, i.e. contain a plurality of rings (such as, for example, decahydronaphthalene or bicyclooctane). Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH₂ groups may be replaced by —O— and/or —S—.

Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1.1.1]-pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, in particular bulky groups, such as, for example, t-butyl or optionally substituted aryl groups.

Preferred substituents, hereinafter also referred to as “L”, are, for example, F, Cl, Br, I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN, —C(═O)N(R^(x))₂, —C(═O)Y¹, —C(═O)R^(x), —N(R^(x))₂, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having 1 to 25 C atoms, in which one or more H atoms may optionally be replaced by F or Cl, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15, C atoms,

wherein R^(x) denotes H, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH₂-groups are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl, P— or P-Sp-, and

Y¹ denotes halogen.

“Substituted silyl or aryl” preferably means substituted by halogen, —CN, R⁰, —OR⁰, —CO—R⁰, —CO—O—R⁰, —O—CO—R⁰ or —O—CO—O—R⁰, wherein R⁰ denotes H or alkyl with 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, Cl, CN, NO₂, CH₃, C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅, furthermore phenyl.

is preferably

in which L has one of the meanings indicated above.

The polymerizable group P is a group which is suitable for a polymerization reaction, such as, for example, free-radical or ionic chain polymerization, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain. Particular preference is given to groups for chain polymerization, in particular those containing a C═C double bond or —C≡C— triple bond, and groups which are suitable for polymerization with ring opening, such as, for example, oxetane or epoxide groups.

Preferred groups P are selected from the group consisting of CH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—(O)_(k3)—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—, CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—, HS—CW²W³—, HW²N—, HO—CW²W³—NH—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—, CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH—, HOOC—, OCN— and W⁴W⁵W⁶Si—, in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k₁, k₂ and k₃ each, independently of one another, denote 0 or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Very preferred groups P are selected from the group consisting of CH₂═CW¹—CO—O—, CH₂═CW¹—CO—,

CH₂═CW²—O—, CH₂═CW²—, CW¹═CH—CO—(O)_(k3)—, CW¹═CH—CO—NH—, CH₂═CW¹—CO—NH—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—, (CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, CH₂═CW¹—CO—NH—, CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—, CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—, Phe-CH═CH— and W⁴W⁵W⁶Si—, in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, k₁, k₂ and k₃ each, independently of one another, denote 0 or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10.

Very particularly preferred groups P are selected from the group consisting of CH₂═CW¹—CO—O—, in particular CH₂═CH—CO—O—, CH₂═C(CH₃)—CO—O— and CH₂═CF—CO—O—, furthermore CH₂═CH—O—, (CH₂═CH)₂CH—O—CO—, (CH₂═CH)₂CH—O—,

Further preferred polymerizable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.

If the spacer group Sp^(a,b) is different from a single bond, it is preferably of the formula Sp″-X″, so that the respective radical P-Sp^(a,b)- conforms to the formula P-Sp″-X″—, wherein

-   Sp″ denotes alkylene having 1 to 20, preferably 1 to 12, C atoms,     which is optionally mono- or polysubstituted by F, Cl, Br, I or CN     and in which, in addition, one or more non-adjacent CH₂ groups may     each be replaced, independently of one another, by —O—, —S—, —NH—,     —N(R⁰)—, —Si(R⁰R⁰⁰)—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —S—CO—,     —CO—S—, —N(R⁰⁰)—CO—O—, —O—CO—N(R⁰)—, —N(R⁰)—CO—N(R⁰⁰)—, —CH═CH— or     —C≡C— in such a way that O and/or S atoms are not linked directly to     one another, -   X″ denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CO—N(R⁰)—,     —N(R⁰)—CO—, —N(R⁰)—CO—N(R⁰⁰)—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—,     —CF₂O—, —OCF₂—, —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,     —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY²═CY³—, —C≡C—, —CH═CH—CO—O—,     —O—CO—CH═CH— or a single bond, -   R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl     having 1 to 20 C atoms, and -   Y² and Y³ each, independently of one another, denote H, F, Cl or CN. -   X″ is preferably —O—, —S—, —CO—, —COO—, —COO—, —O—COO—, —CO—NR⁰—,     —NR⁰—CO—, —NR⁰—CO—NR⁰⁰— or a single bond.

Typical spacer groups Sp and -Sp″-X″— are, for example, —(CH₂)_(p1)—, —(CH₂CH₂O)_(q1)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂—NH—CH₂CH₂— or —(SiR⁰R⁰⁰—O)_(p1)—, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R⁰ and R⁰⁰ have the meanings indicated above.

Particularly preferred groups Sp^(a,b) and -Sp″-X″— are —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—O—CO—, —(CH₂)_(p1)—CO—O—, —(CH₂)_(p1)—O—CO—O—, in which p1 and q1 have the meanings indicated above.

Particularly preferred groups Sp″ are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.

In formula I R preferably denotes H or P-Sp^(b).

Preferred compounds of formula I are selected from the following subformulae

wherein P, Sp^(a), Sp^(b), L and r are as defined in formula I.

Very preferred compounds of formula I are selected from the following subformulae:

wherein P, L and r have the meaning of formula I and Sp¹ is a spacer group.

Further preferred compounds of formula I and its subformulae I1-I4 and I1a-I4a are selected from the following preferred embodiments, including any combination thereof:

-   -   The compounds contain exactly three polymerizable groups         (represented by the groups P),     -   P is selected from the group consisting of acrylate,         methacrylate and oxetane,     -   Sp^(a) and Sp^(b), when being different from a single bond, and         Sp¹ are selected from —(CH₂)_(a)—, —(CH₂)_(a)—O—,         —(CH₂)_(a)—CO—O—, —(CH₂)_(a)—O—CO—, wherein a is 2, 3, 4, 5 or         6, and the O-atom or the CO-group, respectively, is connected to         the benzene ring,     -   L denotes F, Cl, CN, or alkyl or alkoxy with 1 to 6 C atoms that         is optionally fluorinated, very preferably F, Cl, CN, CH₃, OCH₃,         OCF₃, OCF₂H or OCFH₂, most preferably F,     -   r is 0 or 1,     -   s is 0.

Specific preferred compounds are selected from the following formulae

The invention furthermore relates to compounds of formula II

wherein Sp^(a), Sp^(b), L, r and s are as defined in formula I, R denotes H or Pg-Sp^(b), and Pg denotes OH, a protected hydroxyl group or a masked hydroxyl group.

Preferred compounds of formula II are selected from subformulae I1-I4 and I1a-I4a as defined above, wherein P is replaced by Pg.

Suitable protected hydroxyl groups Pg are known to the person skilled in the art. Preferred protecting groups for hydroxyl groups are alkyl, alkoxyalkyl, acyl, alkylsilyl, arylsilyl and arylmethyl groups, especially 2-tetrahydropyranyl, methoxymethyl, methoxyethoxymethyl, acetyl, triisopropylsilyl, tert-butyl-dimethylsilyl or benzyl.

The term “masked hydroxyl group” is understood to mean any functional group that can be chemically converted into a hydroxyl group. Suitable masked hydroxyl groups Pg are known to the person skilled in the art.

The compounds of formula II are suitable as intermediates for the preparation of compounds of the formula I and its subformulae.

The invention further relates to the use of the compounds of formula II as intermediates for the preparation of compounds of the formula I and its subformulae.

The compounds and intermediates of the formulae I and II and sub-formulae thereof can be prepared analogously to processes known to the person skilled in the art and described in standard works of organic chemistry, such as, for example, in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart.

For example, compounds of formula I can be synthesised by esterification or etherification of the intermediates of formula II, wherein Pg denotes OH, using corresponding acids, acid derivatives, or halogenated compounds containing a polymerizable group P.

For example, acrylic or methacrylic esters can be prepared by esterification of the corresponding alcohols with acid derivatives like, for example, (meth)acryloyl chloride or (meth)acrylic anhydride in the presence of a base like pyridine or triethyl amine, and 4-(N,N-dimethylamino)pyridine (DMAP). Alternatively the esters can be prepared by esterification of the alcohols with (meth)acrylic acid in the presence of a dehydrating reagent, for example according to Steglich with dicyclohexylcarbodiimide (DCC), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) or N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride and DMAP.

Further suitable methods are shown in the Examples.

For the production of PSA displays, the polymerizable compounds cointained in the LC medium are polymerized or crosslinked (if one compound contains two or more polymerizable groups) by in-situ polymerization in the LC medium between the substrates of the LC display, optionally while a voltage is applied to the electrodes.

The structure of the PSA displays according to the invention corresponds to the usual geometry for PSA displays, as described in the prior art cited at the outset. Geometries without protrusions are preferred, in particular those in which, in addition, the electrode on the colour filter side is unstructured and only the electrode on the TFT side has slots. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US 2006/0066793 A1.

A preferred PSA type LC display of the present invention comprises:

-   -   a first substrate including a pixel electrode defining pixel         areas, the pixel electrode being connected to a switching         element disposed in each pixel area and optionally including a         micro-slit pattern, and optionally a first alignment layer         disposed on the pixel electrode,     -   a second substrate including a common electrode layer, which may         be disposed on the entire portion of the second substrate facing         the first substrate, and optionally a second alignment layer,     -   an LC layer disposed between the first and second substrates and         including an LC medium comprising a polymerizable component A         and a liquid crystal component B as described above and below,         wherein the polymerizable component A may also be polymerized.

The first and/or second alignment layer controls the alignment direction of the LC molecules of the LC layer. For example, in PS-VA displays the alignment layer is selected such that it imparts to the LC molecules homeotropic (or vertical) alignment (i.e. perpendicular to the surface) or tilted alignment. Such an alignment layer may for example comprise a polyimide, which may also be rubbed, or may be prepared by a photoalignment method.

The LC layer with the LC medium can be deposited between the substrates of the display by methods that are conventionally used by display manufacturers, for example the so-called one-drop-filling (ODF) method. The polymerizable component of the LC medium is then polymerized for example by UV photopolymerization. The polymerization can be carried out in one step or in two or more steps.

The PSA display may comprise further elements, like a colour filter, a black matrix, a passivation layer, optical retardation layers, transistor elements for addressing the individual pixels, etc., all of which are well known to the person skilled in the art and can be employed without inventive skill.

The electrode structure can be designed by the skilled person depending on the individual display type. For example for PS-VA displays a multi-domain orientation of the LC molecules can be induced by providing electrodes having slits and/or bumps or protrusions in order to create two, four or more different tilt alignment directions.

Upon polymerization the polymerizable compounds form a crosslinked polymer, which causes a certain pretilt of the LC molecules in the LC medium. Without wishing to be bound to a specific theory, it is believed that at least a part of the crosslinked polymer, which is formed by the polymerizable compounds, will phase-separate or precipitate from the LC medium and form a polymer layer on the substrates or electrodes, or the alignment layer provided thereon. Microscopic measurement data (like SEM and AFM) have confirmed that at least a part of the formed polymer accumulates at the LC/substrate interface.

The polymerization can be carried out in one step. It is also possible firstly to carry out the polymerization, optionally while applying a voltage, in a first step in order to produce a pretilt angle, and subsequently, in a second polymerization step without an applied voltage, to polymerize or crosslink the compounds which have not reacted in the first step (“end curing”).

Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV induced photopolymerization, which can be achieved by exposure of the polymerizable compounds to UV radiation.

Optionally one or more polymerization initiators are added to the LC medium. Suitable conditions for the polymerization and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerization are, for example, the commercially available photoinitiators Irgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocure1173® (Ciba AG). If a polymerization initiator is employed, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.

The polymerizable compounds according to the invention are also suitable for polymerization without an initiator, which is accompanied by considerable advantages, such, for example, lower material costs and in particular less contamination of the LC medium by possible residual amounts of the initiator or degradation products thereof. The polymerization can thus also be carried out without the addition of an initiator. In a preferred embodiment, the LC medium thus does not contain a polymerization initiator.

The LC medium may also comprise one or more stabilisers in order to prevent undesired spontaneous polymerization of the RMs, for example during storage or transport. Suitable types and amounts of stabilisers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, the commercially available stabilisers from the Irganox® series (Ciba AG), such as, for example, Irganox® 1076. If stabilisers are employed, their proportion, based on the total amount of RMs or the polymerizable component (component A), is preferably 10-500,000 ppm, particularly preferably 50-50,000 ppm.

The polymerizable compounds of formula I do in particular show good UV absorption in, and are therefore especially suitable for, a process of preparing a PSA display including one or more of the following features:

-   -   the polymerizable medium is exposed to UV light in the display         in a 2-step process, including a first UV exposure step (“UV-1         step”) to generate the tilt angle, and a second UV exposure step         (“UV-2 step”) to finish polymerization,     -   the polymerizable medium is exposed to UV light in the display         generated by an energy-saving UV lamp (also known as “green UV         lamps”). These lamps are characterized by a relative low         intensity ( 1/100- 1/10 of a conventional UV1 lamp) in their         absorption spectra from 300-380 nm, and are preferably used in         the UV2 step, but are optionally also used in the UV1 step when         avoiding high intensity is necessary for the process.     -   the polymerizable medium is exposed to UV light in the display         generated by a UV lamp with a radiation spectrum that is shifted         to longer wavelengths, preferably 340 nm or more, to avoid short         UV light exposure in the PS-VA process.

Both using lower intensity and a UV shift to longer wavelengths protect the organic layer against damage that may be caused by the UV light.

A preferred embodiment of the present invention relates to a process for preparing a PSA display as described above and below, comprising one or more of the following features:

-   -   the polymerizable LC medium is exposed to UV light in a 2-step         process, including a first UV exposure step (“UV-1 step”) to         generate the tilt angle, and a second UV exposure step (“UV-2         step”) to finish polymerization,     -   the polymerizable LC medium is exposed to UV light generated by         a UV lamp having an intensity of from 0.5 mW/cm² to 10 mW/cm² in         the wavelength range from 300-380 nm, preferably used in the         UV’step, and optionally also in the UV1 step,     -   the polymerizable LC medium is exposed to UV light having a         wavelength of 340 nm or more, and preferably 400 nm or less.

This preferred process can be carried out for example by using the desired UV lamps or by using a band pass filter and/or a cut-off filter, which are substantially transmissive for UV light with the respective desired wavelength(s) and are substantially blocking light with the respective undesired wavelengths. For example, when irradiation with UV light of wavelengths λ of 300-400 nm is desired, UV exposure can be carried out using a wide band pass filter being substantially transmissive for wavelengths 300 nm<λ<400 nm. When irradiation with UV light of wavelength λ of more than 340 nm is desired, UV exposure can be carried out using a cut-off filter being substantially transmissive for wavelengths λ>340 nm.

“Substantially transmissive” means that the filter transmits a substantial part, preferably at least 50% of the intensity, of incident light of the desired wavelength(s). “Substantially blocking” means that the filter does not transmit a substantial part, preferably at least 50% of the intensity, of incident light of the undesired wavelengths. “Desired (undesired) wavelength” e.g. in case of a band pass filter means the wavelengths inside (outside) the given range of λ, and in case of a cut-off filter means the wavelengths above (below) the given value of λ.

This preferred process enables the manufacture of displays by using longer UV wavelengths, thereby reducing or even avoiding the hazardous and damaging effects of short UV light components.

UV radiation energy is in general from 6 to 100 J, depending on the production process conditions.

Preferably the LC medium according to the present invention does essentially consist of a polymerizable component A), or one or more polymerizable compounds of formula I, and an LC component B), or LC host mixture, as described above and below. However, the LC medium may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, chiral dopants, polymerization initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.

Particular preference is given to LC media comprising one, two or three polymerizable compounds of formula I.

Preference is furthermore given to LC media in which the polymerizable component A) comprises exclusively polymerizable compounds of formula I.

Preference is furthermore given to LC media in which the liquid-crystalline component B) or the LC host mixture has a nematic LC phase, and preferably has no chiral liquid crystal phase.

The LC component B), or LC host mixture, is preferably a nematic LC mixture.

Preference is furthermore given to achiral compounds of formula I, and to LC media in which the compounds of component A and/or B are selected exclusively from the group consisting of achiral compounds.

Preferably the proportion of the polymerizable component A) in the LC medium is from >0 to <5%, very preferably from >0 to <1%, most preferably from 0.01 to 0.5%.

Preferably the proportion of compounds of formula I in the LC medium is from >0 to <5%, very preferably from >0 to <1%, most preferably from 0.01 to 0.5%.

Preferably the proportion of the LC component B) in the LC medium is from 95 to <100%, very preferably from 99 to <100%.

In a preferred embodiment the polymerizable compounds of the polymerizable component B) are exclusively selected from formula I.

In another preferred embodiment the polymerizable component B) comprises, in addition to the compounds of formula I, one or more further polymerizable compounds (“co-monomers”), preferably selected from RMs.

Suitable and preferred mesogenic comonomers are selected from the following formulae:

in which the individual radicals have the following meanings:

-   P¹, P² and P³ each, independently of one another, denote an acrylate     or methacrylate group, -   Sp¹, Sp² and Sp^(a) each, independently of one another, denote a     single bond or a spacer group having one of the meanings indicated     above and below for Sp¹, and particularly preferably denote     —(CH₂)_(p1)—, —(CH₂)_(p1)—O—, —(CH₂)_(p1)—CO—O—, —(CH₂)_(p1)—O—CO—     or —(CH₂)_(p1)—O—CO—O—, in which p1 is an integer from 1 to 12,     where, in addition, one or more of the radicals P¹-Sp¹-, P¹-Sp²- and     P³-Sp³- may denote R^(aa), with the proviso that at least one of the     radicals P¹-Sp¹-, P²-Sp² and P³-Sp³- present is different from     R^(aa), -   R^(aa) denotes H, F, Cl, CN or straight-chain or branched alkyl     having 1 to 25 C atoms, in which, in addition, one or more     non-adjacent CH₂ groups may each be replaced, independently of one     another, by C(R⁰)═C(R⁰⁰)—, —C≡C—, —N(R⁰), —O—, —S—, —CO—, —CO—O—,     —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked     directly to one another, and in which, in addition, one or more H     atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly     preferably straight-chain or branched, optionally mono- or     polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl,     alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12     C atoms (where the alkenyl and alkynyl radicals have at least two C     atoms and the branched radicals have at least three C atoms), -   R⁰, R⁰⁰ each, independently of one another and identically or     differently on each occurrence, denote H or alkyl having 1 to 12 C     atoms, -   R^(y) and R^(z) each, independently of one another, denote H, F, CH₃     or CF₃, -   X¹, X² and X³ each, independently of one another, denote —CO—O—,     —O—CO— or a single bond, -   Z¹ denotes —O—, —CO—, —C(R^(y)R^(z))— or —CF₂CF₂—, -   Z² and Z³ each, independently of one another, denote —CO—O—, —O—CO—,     —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂— or —(CH₂)_(n)—, where n is 2, 3 or 4, -   L on each occurrence, identically or differently, denotes F, Cl, CN     or straight-chain or branched, optionally mono- or poly-fluorinated     alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl,     alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,     preferably F, -   L′ and L″ each, independently of one another, denote H, F or Cl, -   r denotes 0, 1, 2, 3 or 4, -   s denotes 0, 1, 2 or 3, -   t denotes 0, 1 or 2, -   x denotes 0 or 1.

Especially preferred are compounds of formulae M2, M13, M17, M22, M23 and M29.

Further preferred are trireactive compounds M15 to M30, in particular M17, M18, M19, M22, M23, M24, M25, M29 and M30.

In the compounds of formulae M1 to M30 the group

is preferably

wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO₂, CH₃, C₂H₅, C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH₃)C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅ or P-Sp-, very preferably F, Cl, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, more preferably F, Cl, CH₃, OCH₃, COCH₃ order OCF₃, especially F or CH₃.

Besides the polymerizable compounds described above, the LC media for use in the LC displays according to the invention comprise an LC mixture (“host mixture”) comprising one or more, preferably two or more LC compounds which are selected from low-molecular-weight compounds that are unpolymerizable. These LC compounds are selected such that they stable and/or unreactive to a polymerization reaction under the conditions applied to the polymerization of the polymerizable compounds.

In principle, any LC mixture which is suitable for use in conventional displays is suitable as host mixture. Suitable LC mixtures are known to the person skilled in the art and are described in the literature, for example mixtures in VA displays in EP 1 378 557 A1 and mixtures for OCB displays in EP 1 306 418 A1 and DE 102 24 046 A1.

The polymerizable compounds of formula I are especially suitable for use in an LC host mixture that comprises one or more mesogenic or LC compounds comprising an alkenyl group (hereinafter also referred to as “alkenyl compounds”), wherein said alkenyl group is stable to a polymerization reaction under the conditions used for polymerization of the compounds of formula I and of the other polymerizable compounds contained in the LC medium. Compared to RMs known from prior art the compounds of formula I do in such an LC host mixture exhibit improved properties, like solubility, reactivity or capability of generating a tilt angle.

Thus, in addition to the polymerizable compounds of formula I, the LC medium according to the present invention comprises one or more mesogenic or liquid crystalline compounds comprising an alkenyl group, (“alkenyl compound”), where this alkenyl group is preferably stable to a polymerization reaction under the conditions used for the polymerization of the polymerizable compounds of formula I or of the other polymerizable compounds contained in the LC medium.

The alkenyl groups in the alkenyl compounds are preferably selected from straight-chain, branched or cyclic alkenyl, in particular having 2 to 25 C atoms, particularly preferably having 2 to 12 C atoms, in which, in addition, one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F and/or Cl.

Preferred alkenyl groups are straight-chain alkenyl having 2 to 7 C atoms and cyclohexenyl, in particular ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, 1,4-cyclohexen-1-yl and 1,4-cyclohexen-3-yl.

The concentration of compounds containing an alkenyl group in the LC host mixture (i.e. without any polymerizable compounds) is preferably from 5% to 100%, very preferably from 20% to 60%.

Especially preferred are LC mixtures containing 1 to 5, preferably 1, 2 or 3 compounds having an alkenyl group.

The mesogenic and LC compounds containing an alkenyl group are preferably selected from the following formulae:

in which the individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:

-   R^(A1) alkenyl having 2 to 9 C atoms or, if at least one of the     rings X, Y and Z denotes cyclohexenyl, also one of the meanings of     R^(A2), -   R^(A2) alkyl having 1 to 12 C atoms, in which, in addition, one or     two non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,     —OCO— or —COO— in such a way that O atoms are not linked directly to     one another, -   Z^(x) —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,     —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O—, or a single bond, preferably     a single bond, -   L¹⁻⁴ each, independently of one another, H, F, Cl, OCF₃, CF₃, CH₃,     CH₂F or CHF₂H, preferably H, F or Cl, -   x 1 or 2, -   z 0 or 1. -   R^(A2) is preferably straight-chain alkyl or alkoxy having 1 to 8 C     atoms or straight-chain alkenyl having 2 to 7 C atoms.

The LC medium preferably comprises no compounds containing a terminal vinyloxy group (—O—CH═CH₂), in particular no compounds of the formula AN or AY in which R^(A1) or R^(A2) denotes or contains a terminal vinyloxy group (—O—CH═CH₂).

Preferably, L¹ and L² denote F, or one of L¹ and L² denotes F and the other denotes Cl, and L³ and L⁴ denote F, or one of L³ and L⁴ denotes F and the other denotes Cl.

The compounds of the formula AN are preferably selected from the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Very preferred compounds of the formula AN are selected from the following sub-formulae:

in which m denotes 1, 2, 3, 4, 5 or 6, i denotes 0, 1, 2 or 3, and R^(b1) denotes H, CH₃ or C₂H₅.

Very particularly preferred compounds of the formula AN are selected from the following sub-formulae:

Most preferred are compounds of formula AN1a2 and AN1a5.

The compounds of the formula AY are preferably selected from the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Very preferred compounds of the formula AY are selected from the following sub-formulae:

in which m and n each, independently of one another, denote 1, 2, 3, 4, 5 or 6, and alkenyl denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Besides the polymerizable component A) as described above, the LC media according to the present invention comprise an LC component B), or LC host mixture, comprising one or more, preferably two or more LC compounds which are selected from low-molecular-weight compounds that are unpolymerizable. These LC compounds are selected such that they stable and/or unreactive to a polymerization reaction under the conditions applied to the polymerization of the polymerizable compounds.

In a first preferred embodiment the LC medium contains an LC component B), or LC host mixture, based on compounds with negative dielectric anisotropy. Such LC media are especially suitable for use in PS-VA and PS-UB-FFS displays. Particularly preferred embodiments of such an LC medium are those of sections a)-z) below:

-   a) LC medium which comprises one or more compounds of the formulae     CY and/or PY:

-   -   wherein     -   a denotes 1 or 2,     -   b denotes 0 or 1,

-   -    denotes

-   -   R¹ and R² each, independently of one another, denote alkyl         having 1 to 12 C atoms, where, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —OCO— or —COO— in such a way that O atoms are not linked         directly to one another, preferably alkyl or alkoxy having 1 to         6 C atoms,     -   Z^(x) and Z^(y) each, independently of one another, denote         —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—,         —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,         preferably a single bond,     -   L¹⁻⁴ each, independently of one another, denote F, Cl, OCF₃,         CF₃, CH₃, CH₂F, CHF₂.

Preferably, both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes Cl, or both L³ and L⁴ denote F or one of L³ and L⁴ denotes F and the other denotes Cl.

The compounds of the formula CY are preferably selected from the group consisting of the following sub-formulae:

in which a denotes 1 or 2, alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

The compounds of the formula PY are preferably selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   b) LC medium which additionally comprises one or more compounds of     the following formula:

-    in which the individual radicals have the following meanings:

-    denotes

-    denotes

-   -   R³ and R⁴ each, independently of one another, denote alkyl         having 1 to 12 C atoms, in which, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —O—CO— or —CO—O— in such a way that O atoms are not linked         directly to one another,     -   Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,         —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,         preferably a single bond.

The compounds of the formula ZK are preferably selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Especially preferred are compounds of formula ZK1.

Particularly preferred compounds of formula ZK are selected from the following sub-formulae:

wherein the propyl, butyl and pentyl groups are straight-chain groups.

Most preferred are compounds of formula ZK1a.

-   c) LC medium which additionally comprises one or more compounds of     the following formula:

in which the individual radicals on each occurrence, identically or differently, have the following meanings:

-   -   R⁵ and R⁶ each, independently of one another, denote alkyl         having 1 to 12 C atoms, where, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —OCO— or —OCO— in such a way that O atoms are not linked         directly to one another, preferably alkyl or alkoxy having 1 to         6 C atoms,

-   -    denotes

-   -    denotes and

-   -    e denotes 1 or 2.

The compounds of the formula DK are preferably selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   d) LC medium which additionally comprises one or more compounds of     the following formula:

-    in which the individual radicals have the following meanings:

-    denotes

-    with at least one ring F being different from cyclohexylene,     -   f denotes 1 or 2,     -   R¹ and R² each, independently of one another, denote alkyl         having 1 to 12 C atoms, where, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —OCO— or —OCO— in such a way that O atoms are not linked         directly to one another,     -   Z^(x) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—,         —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond,         preferably a single bond,     -   L¹ and L² each, independently of one another, denote F, Cl,         OCF₃, CF₃, CH₃, CH₂F, CHF₂.

Preferably, both radicals L¹ and L² denote F or one of the radicals L¹ and L² denotes F and the other denotes Cl.

The compounds of the formula LY are preferably selected from the group consisting of the following sub-formulae:

in which R¹ has the meaning indicated above, alkyl denotes a straight-chain alkyl radical having 1-6 C atoms, (O) denotes an oxygen atom or a single bond, and v denotes an integer from 1 to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, in particular CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

-   e) LC medium which additionally comprises one or more compounds     selected from the group consisting of the following formulae:

in which alkyl denotes C₁₋₆-alkyl, L^(x) denotes H or F, and X denotes F, Cl, OCF₃, OCHF₂ or OCH═CF₂. Particular preference is given to compounds of the formula G1 in which X denotes F.

-   f) LC medium which additionally comprises one or more compounds     selected from the group consisting of the following formulae:

in which R⁵ has one of the meanings indicated above for R¹, alkyl denotes C₁₋₆-alkyl, d denotes 0 or 1, and z and m each, independently of one another, denote an integer from 1 to 6. R⁵ in these compounds is particularly preferably C₁₋₆-alkyl or -alkoxy or C₂₋₆-alkenyl, d is preferably 1. The LC medium according to the invention preferably comprises one or more compounds of the above-mentioned formulae in amounts of ≦5% by weight.

-   g) LC medium which additionally comprises one or more biphenyl     compounds selected from the group consisting of the following     formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

The proportion of the biphenyls of the formulae B1 to B3 in the LC mixture is preferably at least 3% by weight, in particular ≧5% by weight.

The compounds of the formula B2 are particularly preferred.

The compounds of the formulae B1 to B3 are preferably selected from the group consisting of the following sub-formulae:

in which alkyl* denotes an alkyl radical having 1-6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formulae B1a and/or B2c.

-   h) LC medium which additionally comprises one or more terphenyl     compounds of the following formula:

-    in which R⁵ and R⁶ each, independently of one another, have one of     the meanings indicated above, and

-    each, independently of one another, denote

-    in which L⁵ denotes F or Cl, preferably F, and L⁶ denotes F, Cl,     OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F.

The compounds of the formula T are preferably selected from the group consisting of the following sub-formulae:

in which R denotes a straight-chain alkyl or alkoxy radical having 1-7 C atoms, R* denotes a straight-chain alkenyl radical having 2-7 C atoms, (O) denotes an oxygen atom or a single bond, and m denotes an integer from 1 to 6. R* preferably denotes CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.

The LC medium according to the invention preferably comprises the terphenyls of the formula T and the preferred sub-formulae thereof in an amount of 0.5-30% by weight, in particular 1-20% by weight.

Particular preference is given to compounds of the formulae T1, T2, T3 and T21. In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having 1-5 C atoms.

The terphenyls are preferably employed in mixtures according to the invention if the Δn value of the mixture is to be ≧0.1. Preferred mixtures comprise 2-20% by weight of one or more terphenyl compounds of the formula T, preferably selected from the group of compounds T1 to T22.

-   i) LC medium which additionally comprises one or more quaterphenyl     compounds selected from the group consisting of the following     formulae:

wherein

-   -   R^(Q) is alkyl, alkoxy, oxyalkyl or alkoxyalkyl having 1 to 9 C         atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of         which are optionally fluorinated,     -   X^(Q) is F, Cl, halogenated alkyl or alkoxy having 1 to 6 C         atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C         atoms,     -   L^(Q1) to L^(Q6) independently of each other are H or F, with at         least one of L^(Q1) to L^(Q6) being F.

Preferred compounds of formula Q are those wherein R⁰ denotes straight-chain alkyl with 2 to 6 C-atoms, very preferably ethyl, n-propyl or n-butyl.

Preferred compounds of formula Q are those wherein L^(Q3) and L^(Q4) are F. Further preferred compounds of formula Q are those wherein L^(Q3), L^(Q4) and one or two of L^(Q1) and L^(Q2) are F.

Preferred compounds of formula Q are those wherein X^(Q) denotes F or OCF₃, very preferably F.

The compounds of formula Q are preferably selected from the following subformulae

wherein R⁰ has one of the meanings of formula Q or one of its preferred meanings given above and below, and is preferably ethyl, n-propyl or n-butyl.

Especially preferred are compounds of formula Q1, in particular those wherein R^(Q) is n-propyl.

Preferably the proportion of compounds of formula Q in the LC medium is from >0 to ≦5% by weight, very preferably from 0.1 to 2% by weight, most preferably from 0.2 to 1.5% by weight.

Preferably the LC medium contains 1 to 5, preferably 1 or 2 compounds of formula Q.

The addition of quaterphenyl compounds of formula Q to the LC medium mixture enables to reduce ODF mura, whilst maintaining high UV absorption, enabling quick and complete polymerization, enabling strong and quick tilt angle generation, and increasing the UV stability of the LC medium.

Besides, the addition of compounds of formula Q, which have positive dielectric anisotropy, to the LC medium with negative dielectric anisotropy allows a better control of the values of the dielectric constants ∈_(∥) and ∈_(⊥), and in particular enables to achieve a high value of the dielectric constant ∈_(∥) while keeping the dielectric anisotropy Δ∈ constant, thereby reducing the kick-back voltage and reducing image sticking.

-   k) LC medium which additionally comprises one or more compounds     selected from the group consisting of the following formulae:

-    in which R¹ and R² have the meanings indicated above and preferably     each, independently of one another, denote straight-chain alkyl     having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C     atoms.

Preferred media comprise one or more compounds selected from the formulae O1, O3 and O4.

-   I) LC medium which additionally comprises one or more compounds of     the following formula:

-    in which

-    denotes

R⁹ denotes H, CH₃, C₂H₅ or n-C₃H₇, (F) denotes an optional fluorine substituent, and q denotes 1, 2 or 3, and R⁷ has one of the meanings indicated for R¹, preferably in amounts of >3% by weight, in particular 5% by weight and very particularly preferably 5-30% by weight.

Particularly preferred compounds of the formula FI are selected from the group consisting of the following sub-formulae:

in which R⁷ preferably denotes straight-chain alkyl, and R⁹ denotes CH₃, C₂H₅ or n-C₃H₇. Particular preference is given to the compounds of the formulae FI1, FI2 and FI3.

-   m) LC medium which additionally comprises one or more compounds     selected from the group consisting of the following formulae:

-    in which R⁸ has the meaning indicated for R¹, and alkyl denotes a     straight-chain alkyl radical having 1-6 C atoms. -   n) LC medium which additionally comprises one or more compounds     which contain a tetrahydronaphthyl or naphthyl unit, such as, for     example, the compounds selected from the group consisting of the     following formulae:

in which

-   -   R¹⁰ and R¹¹ each, independently of one another, denote alkyl         having 1 to 12 C atoms, where, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —OCO— or —COO— in such a way that O atoms are not linked         directly to one another, preferably alkyl or alkoxy having 1 to         6 C atoms,     -   and R¹⁰ and R¹¹ preferably denote straight-chain alkyl or alkoxy         having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C         atoms, and     -   Z¹ and Z² each, independently of one another, denote —C₂H₄—,         —CH═CH—, —(CH₂)₄—, —(CH₂)₃O—, —O(CH₂)₃—, —CH═CH—CH₂CH₂—,         —CH₂CH₂CH═CH—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—,         —CF═CH—, —CH═CF—, —CH₂— or a single bond.

-   o) LC medium which additionally comprises one or more     difluorodibenzochromans and/or chromans of the following formulae:

in which

-   -   R¹¹ and R¹² each, independently of one another, have one of the         meanings indicated above for R¹¹,     -   ring M is trans-1,4-cyclohexylene or 1,4-phenylene,     -   Z^(m) —C₂H₄—, —CH₂O—, —OCH₂—, —CO—O— or —O—CO—,     -   c is 0, 1 or 2,

preferably in amounts of 3 to 20% by weight, in particular in amounts of 3 to 15% by weight.

Particularly preferred compounds of the formulae BC, CR and RC are selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, (O) denotes an oxygen atom or a single bond, c is 1 or 2, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Very particular preference is given to mixtures comprising one, two or three compounds of the formula BC-2.

-   p) LC medium which additionally comprises one or more fluorinated     phenanthrenes and/or dibenzofurans of the following formulae:

-    in which R¹¹ and R¹² each, independently of one another, have one     of the meanings indicated above for R¹¹, b denotes 0 or 1, L denotes     F, and r denotes 1, 2 or 3.

Particularly preferred compounds of the formulae PH and BF are selected from the group consisting of the following sub-formulae:

in which R and R′ each, independently of one another, denote a straight-chain alkyl or alkoxy radical having 1-7 C atoms.

-   q) LC medium which additionally comprises one or more monocyclic     compounds of the following formula

wherein

-   -   R¹ and R² each, independently of one another, denote alkyl         having 1 to 12 C atoms, where, in addition, one or two         non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—,         —OCO— or —COO— in such a way that O atoms are not linked         directly to one another, preferably alkyl or alkoxy having 1 to         6 C atoms,     -   L¹ and L² each, independently of one another, denote F, Cl,         OCF₃, CF₃, CH₃, CH₂F, CHF₂.

Preferably, both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes Cl,

The compounds of the formula Y are preferably selected from the group consisting of the following sub-formulae:

in which, Alkyl and Alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, Alkoxy denotes a straight-chain alkoxy radical having 1-6 C atoms, Alkenyl and Alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, and O denotes an oxygen atom or a single bond. Alkenyl and Alkenyl* preferably denote CH₂═CH—, CH₂═CHCH₂CH₂—, CH₃—CH═CH—, CH₃—CH₂—CH═CH—, CH₃—(CH₂)₂—CH═CH—, CH₃—(CH₂)₃—CH═CH— or CH₃—CH═CH—(CH₂)₂—.

Particularly preferred compounds of the formula Y are selected from the group consisting of the following sub-formulae:

wherein Alkoxy preferably denotes straight-chain alkoxy with 3, 4, or 5 C atoms.

-   r) LC medium which, apart from the polymerizable compounds according     to the invention, in particular of the formula I or sub-formulae     thereof and the comonomers, comprises no compounds which contain a     terminal vinyloxy group (—O—CH═CH₂). -   s) LC medium which comprises 1 to 5, preferably 1, 2 or 3,     polymerizable compounds, preferably selected from polymerizable     compounds according to the invention, in particular of the formula I     or sub-formulae thereof. -   t) LC medium in which the proportion of polymerizable compounds, in     particular of the formula I or sub-formulae thereof, in the mixture     as a whole is 0.05 to 5%, preferably 0.1 to 1%. -   u) LC medium which comprises 1 to 8, preferably 1 to 5, compounds of     the formulae CY1, CY2, PY1 and/or PY2. The proportion of these     compounds in the mixture as a whole is preferably 5 to 60%,     particularly preferably 10 to 35%. The content of these individual     compounds is preferably in each case 2 to 20%. -   v) LC medium which comprises 1 to 8, preferably 1 to 5, compounds of     the formulae CY9, CY10, PY9 and/or PY10. The proportion of these     compounds in the mixture as a whole is preferably 5 to 60%,     particularly preferably 10 to 35%. The content of these individual     compounds is preferably in each case 2 to 20%. -   w) LC medium which comprises 1 to 10, preferably 1 to 8, compounds     of the formula ZK, in particular compounds of the formulae ZK1, ZK2     and/or ZK6. The proportion of these compounds in the mixture as a     whole is preferably 3 to 25%, particularly preferably 5 to 45%. The     content of these individual compounds is preferably in each case 2     to 20%. -   x) LC medium in which the proportion of compounds of the formulae     CY, PY and ZK in the mixture as a whole is greater than 70%,     preferably greater than 80%. -   y) LC medium in which the LC host mixture contains one or more     compounds containing an alkenyl group, preferably selected from the     group consisting of formula CY, PY and LY, wherein one or both of R¹     and R² denote straight-chain alkenyl having 2-6 C atoms, formula ZK     and DK, wherein one or both of R³ and R⁴ or one or both of R⁵ and R⁶     denote straight-chain alkenyl having 2-6 C atoms, and formula B2 and     B3, very preferably selected from formulae CY15, CY16, CY24, CY32,     PY15, PY16, ZK3, ZK4, DK3, DK6, B2 and B3, most preferably selected     from formulae ZK3, ZK4, B2 and B3. The concentration of these     compounds in the LC host mixture is preferably from 2 to 70%, very     preferably from 3 to 55%. -   z) LC medium which contains one or more, preferably 1 to 5,     compounds selected of formula PY1-PY8, very preferably of formula     PY2. The proportion of these compounds in the mixture as a whole is     preferably 1 to 30%, particularly preferably 2 to 20%. The content     of these individual compounds is preferably in each case 1 to 20%. -   z1) LC medium which contains one or more, preferably 1, 2 or 3,     compounds of formula T2. The content of these compounds in the     mixture as a whole is preferably 1 to 20%. -   z2) LC medium in which the LC host mixture contains one or more,     preferably 1, 2 or 3, compounds of formula BF1, and one or more,     preferably 1, 2 or 3, compounds selected from formulae AY14, AY15     and AY16, very preferably of formula AY14. The proportion of the     compounds of formula AY14-AY16 in the LC host mixture is preferably     from 2 to 35%, very preferably from 3 to 30%. The proportion of the     compounds of formula BF1 in the LC host mixture is preferably from     0.5 to 20%, very preferably from 1 to 15%. Further preferably the LC     host mixture according to this preferred embodiment contains one or     more, preferably 1, 2 or 3 compounds of formula T, preferably     selected from formula T1, T2 and T5, very preferably from formula T2     or T5. The proportion of the compounds of formula T in the LC host     mixture medium is preferably from 0.5 to 15%, very preferably from 1     to 10%.

In a second preferred embodiment the LC medium contains an LC host mixture based on compounds with positive dielectric anisotropy. Such LC media are especially suitable for use in PS-OCB-, PS-TN-, PS-Posi-VA-, PS-IPS- or PS-FFS-displays.

Particularly preferred is an LC medium of this second preferred embodiment, which contains one or more compounds selected from the group consisting of compounds of formula AA and BB

and optionally contains, in addition to the compounds of formula AA and/or BB, one or more compounds of formula CC

in which the individual radicals have the following meanings:

 each, independently of one another, and on each occurrence, identically or differently

 each, independently of one another, and on each occurrence, identically or differently

-   R²¹, R³¹, R⁴¹, R⁴² each, independently of one another, alkyl,     alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or     alkenyloxy having 2 to 9 C atoms, all of which are optionally     fluorinated, -   X⁰ F, Cl, halogenated alkyl or alkoxy having 1 to 6 C atoms or     halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, -   Z³¹ —CH₂CH₂—, —CF₂CF₂—, —COO—, trans-CH═CH—, trans-CF═CF—, —CH₂O— or     a single bond, preferably —CH₂CH₂—, —COO—, trans-CH═CH— or a single     bond, particularly preferably —COO—,trans-CH═Ch—or a single bond, -   Z⁴¹, Z⁴² —CH₂CH₂—, —COO—, trans-CH═CH—, trans-CF═CF—, —CH₂O—,     —CF₂O—, —C≡C— or a single bond, preferably a single bond, -   L²¹, L²², L³¹, L³² H or F, -   g 0, 1, 2 or 3, -   h 0, 1, 2 or 3. -   X⁰ is preferably F, Cl, CF₃, CHF₂, OCF₃, OCHF₂, OCFHCF₃, OCFHCHF₂,     OCFHCHF₂, OCF₂CH₃, OCF₂CHF₂, OCF₂CHF₂, OCF₂CF₂CHF₂, OCF₂CF₂CHF₂,     OCFHCF₂CF₃, OCFHCF₂CHF₂, OCF₂CF₂CF₃, OCF₂CF₂CClF₂, OCClFCF₂CF₃ or     CH═CF₂, very preferably F or OCF₃

The compounds of formula AA are preferably selected from the group consisting of the following formulae:

in which A²¹, R²¹, X⁰, L²¹ and L²² have the meanings given in formula AA, L²³ and L²⁴ each, independently of one another, are H or F, and X⁰ is preferably F. Particularly preferred are compounds of formulae AA1 and AA2.

Particularly preferred compounds of formula AA1 are selected from the group consisting of the following subformulae:

in which R²¹, X⁰, L²¹ and L²² have the meaning given in formula AA1, L²³, L²⁴, L²⁵ and L²⁶ are each, independently of one another, H or F, and X⁰ is preferably F.

Very particularly preferred compounds of formula AA1 are selected from the group consisting of the following subformulae:

In which R²¹ is as defined in formula AA1.

Very preferred compounds of formula AA2 are selected from the group consisting of the following subformulae:

in which R²¹, X⁰, L²¹ and L²² have the meaning given in formula AA2, L²³, L²⁴, L²⁵ and L²⁶ each, independently of one another, are H or F, and X⁰ is preferably F.

Very particularly preferred compounds of formula AA2 are selected from the group consisting of the following subformulae:

in which R²¹ and X⁰ are as defined in formula AA2.

Particularly preferred compounds of formula AA3 are selected from the group consisting of the following subformulae:

in which R²¹, X⁰, L²¹ and L²² have the meaning given in formula AA3, and X⁰ is preferably F.

Particularly preferred compounds of formula AA4 are selected from the group consisting of the following subformulae:

in which R²¹ is as defined in formula AA4.

The compounds of formula BB are preferably selected from the group consisting of the following formulae:

in which g, A³¹, A³², R³¹, X⁰, L³¹ and L³² have the meanings given in formula BB, and X⁰ is preferably F. Particularly preferred are compounds of formulae BB1 and BB2.

Particularly preferred compounds of formula BB1 are selected from the group consisting of the following subformulae:

in which R³¹, X⁰, L³¹ and L³² have the meaning given in formula BB1, and X⁰ is preferably F.

Very particularly preferred compounds of formula BB1a are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB1.

Very particularly preferred compounds of formula BB1 b are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB1.

Particularly preferred compounds of formula BB2 are selected from the group consisting of the following subformulae:

in which R³¹, X⁰, L³¹ and L³² have the meaning given in formula BB2, L³³, L³⁴, L³⁵ and L³⁶ are each, independently of one another, H or F, and X⁰ is preferably F.

Very particularly preferred compounds of formula BB2 are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2b are selected from the group consisting of the following subformulae

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2c are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2d and BB2e are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2f are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2g are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB2.

Very particularly preferred compounds of formula BB2h are selected from the group consisting of the following subformulae:

in which R³¹ and X⁰ are as defined in formula BB2.

Very particularly preferred compounds of formula BB2i are selected from the group consisting of the following subformulae:

in which R³¹ and X⁰ are as defined in formula BB2.

Very particularly preferred compounds of formula BB2k are selected from the group consisting of the following subformulae:

in which R³¹ and X⁰ are as defined in formula BB2.

Alternatively to, or in addition to, the compounds of formula BB1 and/or BB2 the LC media may also comprise one or more compounds of formula BB3 as defined above.

Particularly preferred compounds of formula BB3 are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula BB3.

Preferably the LC media according to this second preferred embodiment comprise, in addition to the compounds of formula AA and/or BB, one or more dielectrically neutral compounds having a dielectric anisotropy in the range from −1.5 to +3, preferably selected from the group of compounds of formula CC as defined above.

Particularly preferred compounds of formula CC are selected from the group consisting of the following subformulae:

In which R⁴¹ and R⁴² have the meanings given in formula CC, and preferably denote each, independently of one another, alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, and L⁴ is H or F.

Preferably the LC media according to this second preferred embodiment comprise, in addition or alternatively to the dielectrically neutral compounds of formula CC, one or more dielectrically neutral compounds having a dielectric anisotropy in the range from −1.5 to +3, selected from the group of compounds of formula DD.

In which A⁴¹, A⁴², Z⁴¹, Z⁴², R⁴¹, R⁴² and h have the meanings given in formula CC.

Particularly preferred compounds of formula DD are selected from the group consisting of the following subformulae:

in which R⁴¹ and R⁴² have the meanings given in formula DD and R⁴¹ preferably denotes alkyl bedeutet, and in formula DD1 R⁴² preferably denotes alkenyl, particularly preferably —(CH₂)₂—CH═CH—CH₃, and in formula DD2 R⁴² preferably denotes alkyl, —(CH₂)₂—CH═CH₂ or —(CH₂)₂—CH═CH—CH₃.

The compounds of formula AA and BB are preferably used in the LC medium according to the invention in a concentration from 2% to 60%, more preferably from 3% to 35%, and very particularly preferably from 4% to 30% in the mixture as a whole.

The compounds of formula CC and DD are preferably used in the LC medium according to the invention in a concentration from 2% to 70%, more preferably from 5% to 65%, even more preferably from 10% to 60%, and very particularly preferably from 10%, preferably 15%, to 55% in the mixture as a whole.

The combination of compounds of the preferred embodiments mentioned above with the polymerized compounds described above causes low threshold voltages, low rotational viscosities and very good low-temperature stabilities in the LC media according to the invention at the same time as constantly high clearing points and high HR values, and allows the rapid establishment of a particularly low pretilt angle in PSA displays. In particular, the LC media exhibit significantly shortened response times, in particular also the grey-shade response times, in PSA displays compared with the media from the prior art.

The LC media and LC host mixtures of the present invention preferably have a nematic phase range of at least 80 K, particularly preferably at least 100 K, and a rotational viscosity ≦250 mPa·s, preferably ≦200 mPa·s, at 20° C.

In the VA-type displays according to the invention, the molecules in the layer of the LC medium in the switched-off state are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment. On application of an electrical voltage to the electrodes, a realignment of the LC molecules takes place with the longitudinal molecular axes parallel to the electrode surfaces.

LC media according to the invention based on compounds with negative dielectric anisotropy according to the first preferred embodiment, in particular for use in displays of the PS-VA and PS-UB-FFS type, have a negative dielectric anisotropy Δ∈, preferably from −0.5 to −10, in particular from −2.5 to −7.5, at 20° C. and 1 kHz.

The birefringence Δn in LC media according to the invention for use in displays of the PS-VA and PS-UB-FFS type is preferably below 0.16, particularly preferably from 0.06 to 0.14, very particularly preferably from 0.07 to 0.12.

In the OCB-type displays according to the invention, the molecules in the layer of the LC medium have a “bend” alignment. On application of an electrical voltage, a realignment of the LC molecules takes place with the longitudinal molecular axes perpendicular to the electrode surfaces.

LC media according to the invention for use in displays of the PS-OCB, PS-TN, PS-IPS, PS-posi-VA and PS-FFS type are preferably those based on compounds with positive dielectric anisotropy according to the second preferred embodiment, and preferably have a positive dielectric anisotropy Δ∈ from +4 to +17 at 20° C. and 1 kHz.

The birefringence Δn in LC media according to the invention for use in displays of the PS-OCB type is preferably from 0.14 to 0.22, particularly preferably from 0.16 to 0.22.

The birefringence Δn in LC media according to the invention for use in displays of the PS-TN-, PS-posi-VA-, PS-IPS- order PS-FFS-type is preferably from 0.07 to 0.15, particularly preferably from 0.08 to 0.13.

LC media according to the invention, based on compounds with positive dielectric anisotropy according to the second preferred embodiment, for use in displays of the PS-TN-, PS-posi-VA-, PS-IPS- order PS-FFS-type, preferably have a positive dielectric anisotropy Δ∈ from +2 to +30, particularly preferably from +3 to +20, at 20° C. and 1 kHz.

The LC media according to the invention may also comprise further additives which are known to the person skilled in the art and are described in the literature, such as, for example, polymerization initiators, inhibitors, stabilisers, surface-active substances or chiral dopants. These may be polymerizable or non-polymerizable. Polymerizable additives are accordingly ascribed to the polymerizable component or component A). Non-polymerizable additives are accordingly ascribed to the non-polymerizable component or component B).

In a preferred embodiment the LC media contain one or more chiral dopants, preferably in a concentration from 0.01 to 1%, very preferably from 0.05 to 0.5%. The chiral dopants are preferably selected from the group consisting of compounds from Table B below, very preferably from the group consisting of R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, and R- or S-5011.

In another preferred embodiment the LC media contain a racemate of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the previous paragraph.

Furthermore, it is possible to add to the LC media, for example, 0 to 15% by weight of pleochroic dyes, furthermore nanoparticles, conductive salts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate, tetrabutyl-ammonium tetraphenylborate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

The individual components of the preferred embodiments a)-z) of the LC media according to the invention are either known or methods for the preparation thereof can readily be derived from the prior art by the person skilled in the relevant art, since they are based on standard methods described in the literature. Corresponding compounds of the formula CY are described, for example, in EP-A-0 364 538. Corresponding compounds of the formula ZK are described, for example, in DE-A-26 36 684 and DE-A-33 21 373.

The LC media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned compounds with one or more polymerizable compounds as defined above, and optionally with further liquid-crystalline compounds and/or additives. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. The invention furthermore relates to the process for the preparation of the LC media according to the invention.

It goes without saying to the person skilled in the art that the LC media according to the invention may also comprise compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes like deuterium etc.

The following examples explain the present invention without restricting it.

However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective concentrations thereof and combinations thereof with one another. In addition, the examples illustrate which properties and property combinations are accessible.

The following abbreviations are used:

(n, m, z: in each case, independently of one another, 1, 2, 3, 4, 5 or 6)

TABLE A

In a preferred embodiment of the present invention, the LC media according to the invention comprise one or more compounds selected from the group consisting of compounds from Table A.

TABLE B Table B shows possible chiral dopants which can be added to the LC media according to the invention.

C 15

CB 15

CM 21

R/S-811

CM 44

CM 45

CM 47

CN

R/S-2011

R/S-3011

R/S-4011

R/S-5011

R/S-1011

The LC media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight, particularly preferably 0.1 to 3% by weight, of dopants. The LC media preferably comprise one or more dopants selected from the group consisting of compounds from Table B.

TABLE C Table C shows possible stabilisers which can be added to the LC media according to the invention.

(n here denotes an integer from 1 to 12, preferable 1, 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups are not shown).

The LC media preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1% by weight, of stabilisers. The LC media preferably comprise one or more stabilisers selected from the group consisting of compounds from Table C.

TABLE D Table D shows illustrative compounds which can be used in the LC media in accordance with the present invention, preferable as reactive mesogenic compounds.

RM-1

RM-2

RM-3

RM-4

RM-5

RM-6

RM-7

RM-8

RM-9

RM-10

RM-11

RM-12

RM-13

RM-14

RM-15

RM-16

RM-17

RM-18

RM-19

RM-20

RM-21

RM-22

RM-23

RM-24

RM-25

RM-26

RM-27

RM-28

RM-29

RM-30

RM-31

RM-32

RM-33

RM-34

RM-35

RM-36

RM-37

RM-38

RM-39

RM-40

RM-41

RM-42

RM-43

RM-44

RM-45

RM-46

RM-47

RM-48

RM-49

RM-50

RM-51

RM-52

RM-53

RM-54

RM-55

RM-56

RM-57

RM-58

RM-59

RM-60

RM-61

RM-62

RM-63

RM-64

RM-65

RM-66

RM-67

RM-68

RM-69

RM-70

RM-71

In a preferred embodiment of the present invention, the mesogenic media comprise one or more compounds selected from the group of the compounds from Table D.

In addition, the following abbreviations and symbols are used:

-   V₀ threshold voltage, capacitive [V] at 20° C., -   n_(e) extraordinary refractive index at 20° C. and 589 nm, -   n_(o) ordinary refractive index at 20° C. and 589 nm, -   Δn optical anisotropy at 20° C. and 589 nm, -   ∈_(⊥) dielectric permittivity perpendicular to the director at     20° C. and 1 kHz, -   ∈∥ dielectric permittivity parallel to the director at 20° C. and 1     kHz, -   Δ∈ dielectric anisotropy at 20° C. and 1 kHz, -   cl.p., T(N,I) clearing point [° C.], -   γ₁ rotational viscosity at 20° C. [mPa·s], -   K₁ elastic constant, “splay” deformation at 20° C. [pN], -   K₂ elastic constant, “twist” deformation at 20° C. [pN], -   K₃ elastic constant, “bend” deformation at 20° C. [pN].

Unless explicitly noted otherwise, all concentrations in the present application are quoted in percent by weight and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents.

Unless explicitly noted otherwise, all temperature values indicated in the present application, such as, for example, for the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I), are quoted in degrees Celsius (° C.). M.p. denotes melting point, cl.p.=clearing point. Furthermore, C=crystalline state, N=nematic phase, S=smectic phase and I=isotropic phase. The data between these symbols represent the transition temperatures.

All physical properties are and have been determined in accordance with “Merck Liquid Crystals, Physical Properties of Liquid Crystals”, Status Nov. 1997, Merck KGaA, Germany, and apply for a temperature of 20° C., and Δn is determined at 589 nm and Δ∈ at 1 kHz, unless explicitly indicated otherwise in each case.

The term “threshold voltage” for the present invention relates to the capacitive threshold (V₀), also known as the Freedericks threshold, unless explicitly indicated otherwise. In the examples, the optical threshold may also, as generally usual, be quoted for 10% relative contrast (V₁₀).

Unless stated otherwise, the process of polymerising the polymerizable compounds in the PSA displays as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably is carried out at room temperature.

Unless stated otherwise, methods of preparing test cells and measuring their electrooptical and other properties are carried out by the methods as described hereinafter or in analogy thereto.

The display used for measurement of the capacitive threshold voltage consists of two plane-parallel glass outer plates at a separation of 25 μm, each of which has on the inside an electrode layer and an unrubbed polyimide alignment layer on top, which effect a homeotropic edge alignment of the liquid-crystal molecules.

The display or test cell used for measurement of the tilt angles consists of two plane-parallel glass outer plates at a separation of 4 μm, each of which has on the inside an electrode layer and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to one another and effect a homeotropic edge alignment of the liquid-crystal molecules.

The polymerizable compounds are polymerized in the display or test cell by irradiation with UVA light of defined intensity for a prespecified time, with a voltage simultaneously being applied to the display (usually 10 V to 30 V alternating current, 1 kHz). In the examples, unless indicated otherwise, a metal halide lamp and an intensity of 100 mW/cm² is used for polymerization. The intensity is measured using a standard UVA meter (Hoenle UV-meter high end with UVA sensor).

The tilt angle is determined by crystal rotation experiment (Autronic-Melchers TBA-105). A low value (i.e. a large deviation from the 90° angle) corresponds to a large tilt here.

The VHR value is measured as follows: 0.3% of a polymerizable monomeric compound is added to the LC host mixture, and the resultant mixture is introduced into VA-VHR test cells which comprise an unrubbed VA-polyimide alignment layer. The LC-layer thickness d is approx. 6 μm, unless stated otherwise. The VHR value is determined after 5 min at 100° C. before and after UV exposure at 1 V, 60 Hz, 64 μs pulse (measuring instrument: Autronic-Melchers VHRM-105).

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding application No. EP 14002944.8, filed Aug. 25, 2014, are incorporated by reference herein.

EXAMPLE 1

Reactive mesogen 1 is prepared as follows.

1a: To a solution of sodium metaborate tetrahydrate (15.0 g, 53.8 mmol) in dist. water (140 ml) is added the solution of 4-(benzyloxy)phenyl boronic acid (16.00 g, 70.0 mmol) and 3-bromoiodobenzene (25.00 g, 88.0 mmol) in 140 ml THF. After thoroughly degassing with argon, bis(triphenylphosphine)palladium(II) chloride (1.90 g, 2.6 mmol) is added, followed by the addition of hydrazinium hydroxide (0.066 ml, 1.4 mmol). The reaction mixture is heated to reflux and stirred for 5 hours. After cooling to room temperature, the reaction mixture is carefully neutralized with 2 M HCl acid. The aqueous phase is separated and extracted with ethyl acetate. The organic phase is combined and dried over anhydrous sodium sulfate. After removing organic solvent, the oily residue is purified by column chromatography on silica gel with toluene as eluent to afford 1a (26.8 g).

1b: To a solution of 1a (10.00 g, 26.0 mmol) and bis(pinacolato)diboron (12.00 g, 46.3 mmol) in 200 ml 1,4-dioxane was added sodium acetate (6.00 g, 61.1 mmol). After thoroughly degassing with argon, bis(triphenylphosphine)-palladium(II) chloride (1.3 g, 1.78 mmol) is added. The reaction mixture is heated to reflux and stirred for 4 hours. After cooling to room temperature, 200 ml dist. water is added. The aqueous phase is separated and extracted with methyl t-butyl ether. The organic phase is combined and dried over anhydrous sodium sulfate, and filtrated through silica gel. After removing solvent in vacuo, the oily residue is purified by column chromatography on silica gel with toluene as eluent. The obtained crude product is further recrystallized from ethanol to afford 1b (4.7 g).

1c: To a solution of sodium metaborate tetrahydrate (2.60 g, 9.34 mmol) in dist. water (50 ml) is added the solution of 1b (4.70 g, 12.0 mmol) in 50 ml THF. After thoroughly degassing with argon, bis(triphenylphosphine)palladium(II) chloride (0.35 g, 0.49 mmol) is added, followed by the addition of hydrazinium hydroxide (0.011 ml, 0.24 mmol). The reaction mixture is heated to reflux and stirred overnight. After cooling to room temperature, the reaction mixture is carefully neutralized with 2 M HCl acid. The precipitated crude product is recrystallized from toluene/ethyl acetate solvent mixture to afford 1c (1.5 g).

1d: A solution of 1c (1.5 g, 3.82 mmol) in tetrahydrofuran (10 ml) is treated with palladium (5%) on activated charcoal (0.5 g) and submitted to hydrogenation for 20 hs. The catalyst is then filtered off, and the remaining solution is concentrated in vacuo. The residue is recrystallized from toluene/ethyl acetate solvent mixture to provide 1d (0.8 g).

1: 4-(dimethylamino)pyridine (0.033 g, 0.27 mmol) and pyridine (1.0 ml, 12.0 mmol) are added to a suspension of 1d (0.8 g, 2.7 mmol) in dichloromethane (60 ml), to which the solution of methacrylic acid anhydride (1.0 ml, 6.0 mmol) in 10 ml dichloromethane is added dropwise at 5° C. The reaction mixture is stirred for 20 h at room temperature. After removing solvent in vacuo, the oily residue is purified by silica gel chromatography with dichloromethane as eluent. The obtained product is recrystallized from ethanol/diethylether solvent mixture to afford white crystals of 1 (0.4 g, mp. 72° C.).

EXAMPLE 2

Reactive mesogen 2 is prepared as follows.

2a: To a solution of 4-bromo-2-fluorophenol (25.30 g, 128.0 mmol) and bis(pinacolato)diboron (29.00 g, 114.0 mmol) in 300 ml 1,4-dioxane was added potassium acetate (38.00 g, 387.0 mmol). After thoroughly degassing with argon, bis(triphenylphosphine)-palladium(II) chloride (2.8 g, 3.80 mmol) is added. The reaction mixture is heated to reflux and stirred for 4 hours. After cooling to room temperature, 800 ml dist. water is added. The aqueous phase is separated and extracted with methyl t-butyl ether. The organic phase is combined and dried over anhydrous sodium sulfate, and filtrated through silica gel. After removing solvent in vacuo, the oily residue is purified by column chromatography on silica gel with heptane/methyl t-butyl ether 3:2 as eluent. The obtained crude product is further recrystallized from heptane to afford 2a as white crystals (19.9 g).

2b: To a solution of 2a (19.9 g, 83.6 mmol) and 1-bormo-3-iodobenzene (23.48 g, 83.0 mmol) in 200 ml toluene was added 100 ml dist. water and 50 ml ethanol. Sodium carbonate (21.99 g, 207.5 mmol) is added. The resulted suspension is degassed carefully with argon. Tetrakis(triphenylphosphine)palladium(O) (3.44 g, 2.98 mmol) is then added. The reaction mixture is heated to reflux and stirred overnight. After cooling to room temperature, the reaction mixture is neutralized carefully with 6 M HCl acid under cooling to pH˜7. The aqueous phase is extracted with ethylacetate. The organic phase is combined and washed with sat. aq. NaCl solution, dried over sodium sulfate. After removing solvent in vacuo, the solid residue is purified by column chromatography with ethyl acetate/toluene 1:9 as eluent. The crude product is further recrystallized from heptane/ethyl acetate solvent mixture to provide 2b as solid (7.8 g).

2c: To a solution of 2b (7.7 g, 28.8 mmol) in 70 ml ethyl methylketone (EMK) is added potassium carbonate (4.58 g. 33.0 mmol) in several portions. The reaction mixture is heated to 60° C., to which the solution of 3-bromo-1-propanol (4.4 g, 31.7 mmol) in 10 ml EMK is added dropwise. The reaction mixture is stirred 3 hours while refluxing. After cooling to room temperature, the reaction mixture is filtrated. The solid residue is washed thoroughly with aceton. After removing solvent in vacuo, the oily residue is purified by silica gel chromatography with heptane/toluene 7:3 as eluent. The crude product is further recrystallized from heptane/ethyl acetate 4:1 to provide 2c as white solid (7.7 g).

2d: To a solution of sodium metaborate tetrahydrate (5.94 g, 42.6 mmol) in dist. water (20 ml) is added the solution of 2c (7.7 g, 23.6 mmol) and 4-hydroxyphenylboronic acid pinacol ester (5.72 g, 26.0 mmol) in 70 ml THF. After thoroughly degassing with argon, bis(triphenylphosphine)-palladium(II) chloride (0.95 g, 1.3 mmol) is added, followed by the addition of hydrazinium hydroxide (0.05 ml, 1.0 mmol). The reaction mixture is heated to reflux and stirred for 5 hours. After cooling to room temperature, the reaction mixture is carefully neutralized with 2 M HCl acid. The aqueous phase is separated and extracted with ethyl acetate. The organic phase is combined and dried over anhydrous sodium sulfate. After removing organic solvent, the oily residue is purified by column chromatography on silica gel with toluene/ethyl acetate 3:2 as eluent to afford 2d as yellowish solid (6.1 g).

2: Methacrylic acid (3.98 g, 46.3 mmol) and 4-(dimethylamino)pyridine (0.20 g, 1.6 mmol) is added to a suspension of 2d (6.10 g, 17.8 mmol) in dichloromethane (70 ml). The reaction mixture is treated dropwise at 0° C. with a solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (7.47 g, 48.1 mmol) in dichloromethane (70 ml) and stirred for 20 hs at room temperature. The reaction mixture is concentrated in vacuo, and the oily residue is purified by column chromatography on silica gel with heptane/ethyl acetate 7:3 as eluent. The obtained product is recrystallized from heptane/ethanol 1:1 to afford white crystals of 2 (4.0 g, mp. 75° C.).

EXAMPLE 3

Reactive mesogen 3 is prepared as follows.

3a is prepared with the exactly same method as described in 1a.

3b: To a solution of 3a (14.9 g, 42.2 mmol) and 4-hydroxy phenyl boronic acid (6.73 g, 46.4 mmol) in 140 ml 1,4-dioxane was added 35 ml dist. water. Sodium carbonate (8.94 g, 84.3 mmol) is added. The resulted suspension is degassed carefully with argon. Bis(triphenylphosphine)-palladium(II) chloride (0.93 g, 1.26 mmol) is then added. The reaction mixture is heated to reflux and stirred overnight. After cooling to room temperature, the reaction mixture is neutralized carefully with 6 M HCl acid under cooling to pH˜7. The aqueous phase is extracted with ethylacetate. The organic phase is combined and washed with sat. aq. NaCl solution, dried over sodium sulfate. After removing solvent in vacuo, the solid residue is purified by column chromatography with ethyl acetate/toluene 1:9 as eluent. The crude product is further recrystallized from ethanol to provide 3b as brown solid (7.1 g).

3c: To a solution of 3b (7.00 g, 19.6 mmol) in 180 ml dichloromethane are added 4-(dimethylamino)pyridine (0.24 g, 1.96 mmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimidhydrochlorid (DAPECl) (5.24 g, 27.3 mmol). The reaction mixture is stirred at room temperature overnight. 200 ml water is added. The aqueous phase is extracted with dichloromethane. The organic phase is combined and dried over anhydrous sodium sulfate. After removing solvent in vacuo, the solid residue is purified by column chromatography with dichloromethane as eluent to provide 3c as off-white solid (9.06 g).

3d: A solution of 3c (9.0 g, 17.8 mmol) in tetrahydrofuran (90 ml) is treated with palladium (5%) on activated charcoal (1.5 g) and submitted to hydrogenation for 20 hs. The catalyst is then filtered off, and the remaining solution is concentrated in vacuo. The residue is recrystallized from toluene/heptane solvent mixture to provide 3d as white solid (3.8 g).

3: Methacrylic acid (2.95 ml, 34.8 mmol) and 4-(dimethylamino)pyridine (0.14 g, 1.16 mmol) is added to a suspension of 3d (3.80 g, 11.6 mmol) in dichloromethane (40 ml). The reaction mixture is treated dropwise at 0° C. with a solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (5.40 g, 34.8 mmol) in dichloromethane (10 ml) and stirred for 20 hs at room temperature. The reaction mixture is concentrated in vacuo, and the oily residue is purified by column chromatography on silica gel with heptane/ethyl acetate mixture as eluent. The obtained product is recrystallized from heptane/ethanol 1:1 to afford white crystals of 3 (1.6 g, mp. 97° C.).

EXAMPLE 4

Reactive mesogen 4 is prepared as follows.

4b is prepared with the exactly same method as described in 1b.

4c: To a solution of 4b (24.45 g, 63.0 mmol) and 4-bromo benzoic acid (12.8 g, 63.0 mmol) in 210 ml 1,4-dioxane was added 145 ml dist. water. Sodium carbonate (33.4 g, 31.0 mmol) is added. The resulted suspension is degassed carefully with argon. Bis(triphenylphosphine)-palladium(II) chloride (0.88 g, 1.26 mmol) is then added, followed by triphenylphosphine (0.33 g, 1.26 mmol) and triethylamine (0.18 ml, 1.26 mmol). The reaction mixture is heated to reflux and stirred 3 hours. After cooling to room temperature, the reaction mixture is neutralized carefully with 6 M HCl acid under cooling to pH˜7. The precipitated crude product was filtrated and recrystallized from heptane/toluene 1:1 to provide 4c as gray solid (21.8 g).

4d: To a solution of 4c (21.50 g, 55.0 mmol) in DMF (400 ml) is added potassium carbonate (9.17 g, 66.0 mmol). To the resulted suspension (2-bromo-ethoxymethyl)-benzene (19.20 g, 88.0 mmol) is added. The reaction mixture is stirred at 70° C. overnight. After cooling to room temperature, the reaction mixture is added into 1000 ml water and extracted with 3×300 ml ethyl acetate. The organic phase is washed with sat. aq. NaCl solution, dried over sodium sulfate. After removing solvent in vacuo, the oily residue is purified by column chromatography on silica gel with dichloromethane as eluent to provide 4d as white crystal (23.9 g).

4e: A suspension of 4d (23.9 g, 45.0 mmol) in tetrahydrofuran (240 ml) is treated with palladium (5%) on activated charcoal (6.0 g) and submitted to hydrogenation for 30 hs. The catalyst is then filtered off. After removing solvent in vacuo, the solid residue is purified by column chromatography on silica gel with toluene/heptane 1:1 as elute to provide 4c as white solid (13.8 g).

4: Methacrylic acid (5.33 ml, 62.0 mmol) and 4-(dimethylamino)pyridine (0.26 g, 2.1 mmol) is added to a suspension of 4e (7.00 g, 20.0 mmol) in dichloromethane (90 ml). The reaction mixture is treated dropwise at 0° C. with a solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (9.75 g, 62.0 mmol) in dichloromethane (20 ml) and stirred for 20 hs at room temperature. The reaction mixture is concentrated in vacuo, and the oily residue is purified by column chromatography on silica gel with dichloromethane as eluent. The obtained product is recrystallized from ethyl acetate/heptane 1:2 to afford white crystals of 4 (4.7 g, mp. 72° C.).

In analogy to the methods described in Example 4, the following two compounds are prepared.

EXAMPLE 5

EXAMPLE 6

EXAMPLE 7

Reactive mesogen 7 is prepared as follows.

7b is prepared by the same method as described for compound 1b in Example 1.

7c: To a solution of 4-bromoresorcinol (30.0 g, 15.0 mmol) in DMF (250 ml) is added potassium carbonate (4.32 g, 31.0 mmol). To the resulted suspension ethylene carbonate (34.20 g, 39.0 mmol) is added. The reaction mixture is heated to reflux and stirred overnight. After cooling to room temperature, the reaction mixture is added into 1000 ml water and extracted with 3×300 ml ethyl acetate. The organic phase is washed with sat. aq. NaCl solution, dried over sodium sulfate. After removing solvent in vacuo, the oily residue is purified by column chromatography on silica gel with ethylacetate as eluent to provide 7c as white crystal (31.3 g).

7d: To a solution of 7b (14.27 g, 36.0 mol) and 7c (9.4 g, 33.0 mmol) in 400 ml 1,4-dioxane was added 38.5 g (167.0 mmol) potassium phosphate. The resulted suspension is degassed carefully with argon. Tris(dibenzylidene acetone)dipalladium(0) (0.61 g, 0.67 mmol) and 2-dicyclohexylphosphine-2′,6′-dimethoxylbiphenyl (SPhos) (1.13 g, 2.68 mmol) is then added. The reaction mixture is heated to reflux and stirred overnight. After cooling to room temperature 700 ml dist. water and 300 ml ethylacetate are added, and the mixture is neutralized carefully with 6 M HCl acid under cooling to pH˜4. The aqueous phase is extracted with ethylacetate. The organic phase is combined and washed with sat. aq. NaCl solution, dried over sodium sulfate. After removing solvent in vacuo, the solid residue is purified by column chromatography with ethyl acetate as eluent to provide 7d as light brown solid (8.5 g).

7e: A suspension of 7d (8.4 g, 18.1 mmol) in tetrahydrofuran (80 ml) is treated with palladium (5%) on activated charcoal (1.5 g) and submitted to hydrogenation for 20 hs. The catalyst is then filtered off. After removing solvent in vacuo, the solid residue is purified by column chromatography on silica gel with THF as elute to provide 7e as yellowish oil (7.7 g).

7: Methacrylic acid (4.50 ml, 53.0 mmol) and 4-(dimethylamino)pyridine (0.16 g, 1.3 mmol) is added to a suspension of 7e (5.00 g, 13.2 mmol) in dichloromethane (50 ml). The reaction mixture is treated dropwise at 0° C. with a solution of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (8.23 g, 53.0 mmol) in dichloromethane (20 ml) and stirred for 20 hs at room temperature. The reaction mixture is concentrated in vacuo, and the oily residue is purified by column chromatography on silica gel with dichloromethane as eluent. The obtained product is recrystallized from ethanol/heptane 6:1 to afford white crystals of 7 (4.1 g, mp. 83° C.).

MIXTURE EXAMPLE 1

The nematic LC host mixture 1 is formulated as follows.

CCH-501 9.00% cl.p. 70.0° C. CCH-35 14.00% Δn 0.0825 PCH-53 8.00% Δε −3.5 PCH-304FF 14.00% ε_(||) 3.5 PCH-504FF 13.00% K₃/K₁ 1.00 CCP-302FF 8.00% γ₁ 141 mPa s CCP-502FF 8.00% V₀ 2.10 V CCP-21FF 9.00% CCP-31FF 9.00% CPY-2-O2 8.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 1 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 2

The nematic LC host mixture 2 is formulated as follows.

CY-3-O2 18.00% cl.p. +74.5° C. CPY-2-O2 10.00% Δn 0.1021 CPY-3-O2 10.00% Δε −3.1 CCY-3-O2 9.00% ε_(||) 3.5 CCY-4-O2 4.00% K₃/K₁ 1.16 CC-3-V 40.00% γ₁ 86 mPa s PYP-2-3 9.00% V₀ 2.29 V

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 2 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 3

The nematic LC host mixture 3 is formulated as follows.

CC-3-V 20.00% cl.p. 74.5° C. CC-3-V1 10.00% Δn 0.1084 CCH-34 8.00% Δε −3.2 CCH-35 4.00% V₀ 2.33 V CCY-3-O1 5.50% K₃/K₁ 1.04 CCY-3-O2 12.00% γ₁ 94 mPa s CPY-2-O2 2.00% CPY-3-O2 12.00% PY-3-O2 15.00% PY-4-O2 8.50% PYP-2-3 3.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 3 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 4

The nematic LC host mixture 4 is formulated as follows.

CC-3-V 20.00% cl.p. 74.6° C. CC-3-V1 10.00% Δn 0.1042 CCH-35 9.00% Δε −3.1 CCP-3-1 7.00% V₀ 2.48 V CCY-3-O2 13.00% K₃/K₁ 1.13 CPY-3-O2 13.00% γ₁ 94 mPa s CY-3-O2 8.00% PY-3-O2 15.00% PY-4-O2 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 4 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 5

The nematic LC host mixture 5 is formulated as follows.

CC-3-V 27.50% cl.p. 74.8° C. CC-3-V1 7.50% Δn 0.0986 CCH-23 3.00% Δε −3.4 CCP-3-1 3.75% V₀ 2.26 V CCY-3-O2 12.50% K₃/K₁ 1.16 CPY-2-O2 11.50% γ₁ 95 mPa s CPY-3-O2 10.50% CY-3-O2 15.50% PY-3-O2 3.00% PY-4-O2 5.25%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 5 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 6

The nematic LC host mixture 6 is formulated as follows.

CC-3-V 41.50% cl.p. 74.6° C. CCP-3-1 2.00% Δn 0.0983 CCY-3-O1 5.25% Δε −3.1 CCY-3-O2 12.50% V₀ 2.28 V CPY-2-O2 12.25% K₃/K₁ 1.11 CPY-3-O2 7.50% γ₁ 85 mPa s CY-3-O2 5.50% PY-3-O2 3.50% PY-4-O2 10.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 6 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 7

The nematic LC host mixture 7 is formulated as follows.

CC-3-V 27.50% cl.p. 75.6° C. CC-3-V1 8.00% Δn 0.0989 CCH-23 2.50% Δε −3.4 CCP-3-1 3.00% V₀ 2.28 V CCY-3-O2 12.00% K₃/K₁ 1.16 CCY-4-O2 2.00% γ₁ 94 mPa s CPY-2-O2 10.00% CPY-3-O2 10.50% CY-3-O2 15.50% CY-3-O4 1.00% PY-3-O2 15.00% PY-4-O2 7.00% PYP-2-3 1.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 7 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 8

The nematic LC host mixture 8 is formulated as follows.

CC-3-V 41.50% cl.p. 74.5° C. CCY-3-O1 2.50% Δn 0.0984 CCY-3-O2 11.50% Δε −3.3 CCY-3-O3 5.00% V₀ 2.29 V CPY-2-O2 5.00% K₃/K₁ 1.15 CPY-3-O2 12.00% γ₁ 89 mPa s CY-3-O2 9.50% PY-3-O2 7.00% PY-4-O2 3.00% PYP-2-3 3.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 8 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 9

The nematic LC host mixture 9 is formulated as follows.

CC-3-V 28.00% cl.p. 74.9° C. CCY-3-O1 10.00% Δn 0.1026 CCY-3-O2 1.00% Δε −3.0 CCY-3-O3 6.00% V₀ 2.47 V CPY-2-O2 12.00% K₃/K₁ 1.19 CPY-3-O2 3.00% γ₁ 90 mPa s CY-3-O2 12.00% PY-3-O2 10.00% PY-4-O2 15.00% PYP-2-3 3.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 9 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 10

The nematic LC host mixture 10 is formulated as follows.

CC-3-V 15.00% cl.p. 74.4° C. CC-3-V1 9.00% Δn 0.1086 CCH-23 8.00% Δε −3.2 CCH-34 7.50% V₀ 2.33 V CCY-3-O2 10.00% K₃/K₁ 1.10 CCY-5-O2 8.00% γ₁ 102 mPa s CPY-2-O2 3.00% CPY-3-O2 8.50% CY-3-O2 7.00% PY-3-O2 16.00% PYP-2-3 8.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 10 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 11

The nematic LC host mixture 11 is formulated as follows.

CC-3-V 42.00% cl.p. 73.5° C. CCY-3-O1 5.00% Δn 0.1007 CCY-3-O2 10.00% Δε −3.5 CCY-4-O2 2.50% V₀ 2.15 V CPY-2-O2 10.00% K₃/K₁ 1.13 CPY-3-O2 10.00% γ₁ 85 mPa s CY-3-O2 6.50% PY-3-O2 11.00% IS-18566 3.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 11 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 12

The nematic LC host mixture 12 is formulated as follows.

CC-3-V 45.50% cl.p. 73.0° C. CCY-3-O1 3.00% Δn 0.1011 CCY-3-O2 11.00% Δε −3.5 CCY-4-O2 3.50% V₀ 2.15 V CPY-2-O2 7.50% K₃/K₁ 1.09 CPY-3-O2 10.00% γ₁ 79 mPa s CY-3-O2 2.00% PY-3-O2 11.50% IS-18566 6.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 12 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 13

The nematic LC host mixture 13 is formulated as follows.

CC-3-V 34.50% cl.p. 75.0° C. CC-3-V1 8.00% Δn 0.1075 CCY-3-O1 7.00% Δε −3.1 CCY-3-O2 11.50% V₀ 2.41 V CCY-4-O2 3.50% K₃/K₁ 1.12 CPY-3-O2 11.50% γ₁ 84 mPa s PY-3-O2 13.00% PP-1-2V1 6.00% IS-18566 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 13 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 14

The nematic LC host mixture 14 is formulated as follows.

CC-3-V 37.50% cl.p. 75.5° C. CC-3-V1 7.00% Δn 0.1080 CCY-3-O1 6.00% Δε −3.0 CCY-3-O2 11.00% V₀ 2.41 V CPY-2-O2 4.50% K₃/K₁ 1.12 CPY-3-O2 11.00% γ₁ 84 mPa s PY-3-O2 17.00% PGIY-2-O4 5.00% PP-1-2V1 1.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 14 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 15

The nematic LC host mixture 15 is formulated as follows.

CC-3-V 39.00% cl.p. 75.0° C. CC-3-V1 7.00% Δn 0.1098 CCY-3-O1 1.50% Δε −3.0 CCY-3-O2 5.00% V₀ 2.41 V CPY-2-O2 9.00% K₃/K₁ 1.11 CPY-3-O2 6.00% γ₁ 82 mPa s PY-3-O2 11.50% PGIY-2-O4 16.00% PP-1-2V1 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 15 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 16

The nematic LC host mixture 16 is formulated as follows.

CY-3-O2 16.50% cl.p. 74.0° C. CCY-4-O2 10.50% Δn 0.1069 CCY-5-O2 6.00% Δε −3.2 CPY-2-O2 9.00% V₀ 2.18 CPY-3-O2 9.00% K₃/K₁ 1.06 CCH-34 9.00% γ₁ 117 mPa s CCH-31 20.00% CCP-3-1 2.00% PYP-2-3 6.50% PYP-2-4 6.50% PCH-301 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 16 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 17

The nematic LC host mixture 17 is formulated as follows.

CY-3-O2 16.50% cl.p. 74.5° C. CCY-4-O2 9.50% Δn 0.1070 CCY-5-O2 4.00% Δε −3.2 CPY-2-O2 9.00% V₀ 2.19 CPY-3-O2 9.00% K₃/K₁ 1.06 CCH-34 9.00% γ₁ 117 mPa s CCH-31 20.00% CCP-3-1 5.00% PYP-2-3 4.00% PYP-2-4 4.00% PCH-301 5.00% PGIY-2-O4 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 17 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 18

The nematic LC host mixture 18 is formulated as follows.

CY-3-O2 12.00% cl.p. 74.0° C. CY-3-O4 10.00% Δn 0.1064 CCY-3-O2 6.00% Δε −3.2 CCY-4-O2 6.50% V₀ 2.19 CCH-34 9.00% K₃/K₁ 0.99 CCH-35 5.00% γ₁ 119 mPa s CCP-3-1 14.50% CCP-3-3 11.00% PYP-2-3 9.00% PYP-2-4 8.00% Y-4O-O4 9.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 18 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 19

The nematic LC host mixture 19 is formulated as follows.

CY-3-O2 12.00% cl.p. 73.5° C. CY-3-O4 10.00% Δn 0.1065 CCY-3-O2 6.00% Δε −3.3 CCY-4-O2 5.50% V₀ 2.18 CCH-34 8.50% K₃/K₁ 1.00 CCH-35 5.00% γ₁ 119 mPa s CCP-3-1 15.00% CCP-3-3 11.50% PYP-2-3 5.50% PYP-2-4 5.00% PP-1-2V1 2.00% PGIY-2-O4 5.00% Y-4O-O4 9.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 19 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 20

The nematic LC host mixture 20 is formulated as follows.

CC-3-V 28.50% cl.p. 74.5° C. CCP-31 12.50% Δn 0.1077 CCOY-2-O2 19.00% Δε −3.2 CCOY-3-O2 11.50% V₀ 2.34 V PY-3-O2 13.50% K₃/K₁ 0.91 PP-1-3 10.00% γ₁ 99 mPa s PYP-2-3 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 20 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 21

The nematic LC host mixture 21 is formulated as follows.

CC-3-V1 9.00% cl.p. 75.4° C. CCH-23 14.00% Δn 0.1056 CCH-34 6.00% Δε −2.8 CCH-35 6.00% V₀ 2.67 V CCP-3-1 7.00% K₃/K₁ 1.07 CCY-3-O1 5.00% γ₁ 102 mPa s CCY-3-O2 10.00% CPY-3-O2 12.00% CY-3-O2 9.50% PP-1-2V1 8.50% PY-3-O2 12.00% PY-4-O2 1.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 21 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 22

The nematic LC host mixture 22 is formulated as follows.

CC-3-V 37.00% cl.p. 75.0° C. CC-3-V1 7.00% Δn 0.1090 CCY-3-O2 5.00% Δε −3.2 CLY-3-O2 10.00% V₀ 2.34 V CPY-2-O2 10.50% K₃/K₁ 1.14 CPY-3-O2 10.50% γ₁ 87 mPa s PY-1-O4 10.00% PY-3-O2 9.00% PGIY-2-O4 1.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 22 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 23

The nematic LC host mixture 23 is formulated as follows.

CC-3-V 34.50% cl.p. 74.5° C. CC-3-V1 8.00% Δn 0.1088 CCY-3-O1 9.00% Δε −3.2 CCY-3-O2 5.50% V₀ 2.33 V CLY-3-O2 10.00% K₃/K₁ 1.12 CPY-3-O2 5.00% γ₁ 90 mPa s PY-1-O4 10.00% PY-3-O2 10.00% PYP-2-3 3.00% PGIY-2-O4 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 23 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 24

The nematic LC host mixture 24 is formulated as follows.

B-2O-O5 5.00% cl.p. 74.6° C. CC-3-V1 38.00% Δn 0.1086 CCY-3-O1 10.00% Δε −3.2 CCY-3-O2 7.50% V₀ 2.34 V CLY-3-O2 10.00% K₃/K₁ 1.11 CPY-3-O2 9.50% γ₁ 82 mPa s PY-3-O2 13.00% PYP-2-3 2.00% PGIY-2-O4 5.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 24 at a concentration of 0.3% by weight.

MIXTURE EXAMPLE 25

The nematic LC host mixture 25 is formulated as follows.

CC-3-V 34.00% cl.p. 74.3° C. CC-3-V1 10.00% Δn 0.1091 CCY-3-O1 4.50% Δε −3.2 CLY-3-O2 10.00% V₀ 2.34 V CPY-2-O2 10.50% K₃/K₁ 1.12 CPY-3-O2 11.00% γ₁ 88 mPa s PY-1-O4 9.00% PY-3-O2 11.00%

Four polymerizable mixtures are prepared by adding each one of RM1 to RM4, respectively, to nematic LC host mixture 25 at a concentration of 0.3% by weight.

For comparison purposes further individual polymerizable mixtures are prepared by adding direactive monomer Cl of prior art to each of nematic LC host mixtures 1-25 at a concentration of 0.3% by weight, respectively.

USE EXAMPLES

The polymerizable mixtures according to the invention and the polymerizable comparison mixtures are each inserted into a VA e/o test cell. The test cells comprise a VA-polyimide alignment layer (JALS-2096-R¹) which is rubbed antiparallel. The LC-layer thickness d is approx. 4 μm.

Each test cell is irradiated with UV light having an intensity of 100 mW/cm² for the time indicated with application of a voltage of 24 V_(rms) (alternating current), causing polymerization of the polymerizable monomeric compound.

The VHR values of the polymerizable mixtures before and after UV exposure are measured as described above. The VHR values of the mixtures are shown in Table 1.

TABLE 1 VHR values Host Host Host Host Host Host 1 + 1 + 1 + 1 + 1 + 1 + C1 RM1 RM2 RM3 RM4 RM5 VHR/% 0 min UV 98.2 98.2 98.9 98.2 99.0 98.9 2 h 98.1 98.2 98.6 98.2 98.8 98.9 Suntest¹⁾ Host Host Host Host Host Host 2 + 2 + 2 + 2 + 2 + 1 + C1 RM1 RM2 RM3 RM4 RM5 VHR/% 0 min UV 96.4 97.1 98.2 98.4 98.7 98.7 2 h 86.5 84.2 89.8 89.6 91.5 95.0 Suntest¹⁾ 10 min UV 79.6 84.0 87.7 88.6 89.9 94.4 ¹⁾“Suntest” means a second irradiation step with lower UV intensity but longer exposure time than the first step.

As can be seen from Table 1, the VHR values of polymerizable mixtures comprising RM1 to RM5 according to the present invention after UV exposure are higher than the VHR values of polymerizable mixture comprising monomer C1, especially in polymerizable mixtures comprising host mixture 2 with alkenyl compounds.

In addition, RM1 to RM5 according to the present invention do either show only a very small decrease or even an increase of the VHR after 2h suntest compared to the initial VHR value.

In order to determine the polymerization rate, the residual content of unpolymerized RM (in % by weight) in the test cells is measured by HPLC after various exposure times. For this purpose each mixture is polymerized in the test cell under the stated conditions. The mixture is then rinsed out of the test cell using MEK (methyl ethyl ketone) and measured.

The residual concentrations of the respective monomer in the mixture after different exposure times are shown in Table 2.

TABLE 2 Residual monomer content Host 1 + Host 1 + Host 1 + Time/ C1 RM4 RM5 min Residual RM/% 0 0.300 0.300 0.300 2 0.268 0.241 0.242 4 0.236 0.158 0.153 6 0.200 0.132 0.133 Host 2 + Host 2 + Host 2 + Time/ C1 RM4 RM5 min Residual RM/% 0 0.300 0.300 0.300 2 0.219 0.205 0.192 6 0.107 0.088 0.072

As can be seen from Table 2, significantly more rapid and complete polymerization is achieved in PSA displays containing a polymerizable mixture with RM4 or RM5 according to the present invention, compared to PSA displays containing a polymerizable mixture with monomer Cl.

The tilt angle is determined before and after UV irradiation by a crystal rotation experiment (Autronic-Melchers TBA-105).

The tilt angles are shown in Table 3.

TABLE 3 Tilt angles Host Host Host + Host 1 + Host 1 + Host 1 + 1 + 1 + UV-Time/ C1 RM1 RM2 RM3 RM4 RM5 sec Pretilt Angle/° 0 89.0 88.6 88.5 88.6 89.2 89.0 30 88.8 88.8 86.9 87.4 88.2 88.8 60 87.8 87.4 86.5 86.0 86.1 86.7 120 86.2 80.6 83.9 77.7 78.1 80.1 Host Host Host 2 + Host 2 + Host 2 + Host 2 + 2 + 2 + UV-Time/ C1 RM1 RM2 RM3 RM4 RM5 sec Pretilt Angle/° 0 88.8 87.7 88.5 88.6 89.0 89.0 120 80.7 80.5 79.4 79.8 77.7 75.0

As can be seen from Table 3, a small tilt angle after polymerization is achieved quickly in PSA displays containing a polymerizable mixture with RM1 to RM5 according to the present invention, which is smaller than in a PSA display containing a polymerizable mixture with monomer C1.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

The invention claimed is:
 1. A compound of formula I

wherein R denotes P-Sp^(b)-, H or has one of the meanings given for L, Sp^(a), Sp^(b) denote, on each occurrence identically or differently, a spacer group or a single bond, P denotes, on each occurrence identically or differently, a polymerizable group, L F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH₂-groups are optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, r is 0, 1, 2, 3 or 4, s is 0, 1, 2 or 3, wherein at least one of the groups Sp^(a) and Sp^(b) is a single bond and at least one of the groups Sp^(a) and Sp^(b) is different from a single bond.
 2. The compound of claim 1, wherein R is H or P-Sp^(b).
 3. The compound of claim 1, of the formula:


4. The compound according to claim 1, of the formula:

wherein Sp¹ is a spacer group.
 5. The compound according to claim 1, wherein P is an acrylate, methacrylate or oxetane.
 6. The compound according to claim 1, wherein Sp¹, and Sp^(a) and Sp^(b) if not a single bond, are —(CH₂)_(a)—, —(CH₂)_(a)—O—, —(CH₂)_(a)—CO—O—, or —(CH₂)_(a)—O—CO—, wherein a is 2, 3, 4, 5 or 6, and the O-atom or the CO-group, respectively, is connected to the aromatic ring.
 7. A liquid crystal (LC) medium comprising one or more polymerizable compounds formula I as defined in claim
 1. 8. The LC medium of claim 7, comprising a polymerizable component A) comprising one or more polymerizable compounds of formula I, and a liquid-crystalline LC component B) comprising one or more mesogenic or liquid-crystalline compounds.
 9. The LC medium of claim 7, comprising one or more compounds of the formulae CY and/or PY:

wherein a denotes 1 or 2, b denotes 0 or 1,

 denotes

R¹ and R² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—, —OCO— or —OCO— in such a way that O atoms are not linked directly to one another, Z^(x) and Z^(y) each, independently of one another, denote —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond, and L¹⁻⁴ each, independently of one another, denote F, Cl, OCF₃, CF₃, CH₃, CH₂F, CHF₂.
 10. The LC medium according to claim 7, comprising one or more compounds of the following formulae:

in which individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:

R^(A1) alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z denotes cyclohexenyl, also one of the meanings of R^(A2), R^(A2) alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—, —OCO— or —COO— in such a way that O atoms are not linked directly to one another, Z^(x) —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —O₂F₄—, —CF═CF—, —CH═CH—CH₂O—, or a single bond, L¹⁻⁴ each, independently of one another, H, F, Cl, OCF₃, CF₃, CH₃, CH₂F or CHF₂H, x 1 or 2, and z 0 or
 1. 11. The LC medium according to claim 7, comprising one or more compounds of the following formula:

in which individual radicals have the following meanings:

 denotes

 denotes

R³ and R⁴ each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by —O—, —CH═CH—, —CO—, —O—CO— or —CO—O— in such a way that O atoms are not linked directly to one another, Z^(y) denotes —CH₂CH₂—, —CH═CH—, —CF₂O—, —OCF₂—, —CH₂O—, —OCH₂—, —CO—O—, —O—CO—, —C₂F₄—, —CF═CF—, —CH═CH—CH₂O— or a single bond.
 12. The LC medium according to claim 7, wherein the polymerizable compounds of formula I are polymerized.
 13. A process of preparing an LC medium of claim 7, comprising mixing one or more mesogenic or liquid-crystalline compounds, with one or more compounds of formula I, and optionally with further liquid-crystalline compounds and/or additives.
 14. An LC display comprising one or more compounds of formula I as defined in claim
 1. 15. The LC display of claim 14, which is a PSA display.
 16. The LC display of claim 15, which is a PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB-FFS, PS-posi-VA or PS-TN display.
 17. The LC display of claim 15, comprising two substrates, at least one which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and located between the substrates a layer of an LC medium, comprising one or more polymerizable compounds of formula I, wherein the polymerizable compounds are polymerized between the substrates of the display.
 18. A process for the production of an LC display according to claim 17, comprising providing an LC medium, comprising one or more polymerizable compounds, of formula I, between the substrates of the display, and polymerizing the polymerizable compounds.
 19. A compound according to claim 1, of formula II

R′ denotes H or Pg-Sp^(b), and Pg denotes OH, a protected hydroxyl group or a masked hydroxyl group.
 20. A process for preparing a compound of formula I of claim 1, wherein P denotes acrylate or methacrylate, by esterification of a compound of formula II

wherein Pg denotes OH, and R′ denotes H or Pg-Sp^(b) using corresponding acids, acid derivatives, or halogenated compounds containing a group P, in the presence of a dehydrating reagent. 